13 (number)

''"Thirteen" redirects here.

See also Thirteen, a 2003 movie; 13, an album by British band Blur; Thirteen, an album by Teenage Fanclub.

13 (thirteen) is the natural number following 12 and preceding 14. It is the smallest integer with eight letters in its spelled out name in English.


Cardinal	13 thirteen
Ordinal	13th thirteenth
Numeral system	tredecimal
Factorization	prime
Divisors	1, 13
Roman numeral	XIII
Binary	1101
Hexadecimal	D

In mathematics

Thirteen is the 6th smallest prime number; the next is seventeen. 13 is the second Wilson prime. 13 is the fifth Mersenne prime exponent, yielding 8191. 13 is also the third lucky prime.

13 is the second star number and the seventh Fibonacci number. As it is an odd-indexed Fibonacci number, it is a Markov number, appearing in solutions to the Markov Diophantine equation: (1, 5, 13), (1, 13, 34), (5, 13, 194), ...

There are 13 Archimedean solids.

13 goes into 999,999 exactly 76,923 times, so vulgar fractions with 13 in the denominator have six digit repeating sequences in their decimal expansions.

At 13, the Mertens function sets a new low of -3, subseded later at 31 with a value of -4.

13 is the only positive integer that is the fourth root of the sum of the squares of two successive positive integers (119 and 120).

The 13th root is the most famous integer root calculation record, because 13 is the first prime number over 10 such as the last digit of a 13th integer power is the same as the last digit of its 13th root.

In base 10, the smallest prime with a composite sum of digits is 13.

13 is a repdigit in base 3 (111).

In science

The atomic number of aluminium
The number of dimensions in some theories of relativity

Astronomy

Messier object M13, a magnitude 7.0 globular cluster in the constellation Hercules, also known as the Hercules cluster. It is one of the brightest and best-known of the globular clusters.

The New General Catalogue object NGC 13, a spiral galaxy in the constellation Andromeda

The Saros number of the solar eclipse series which began on -2561 September 12 and ended on -1046 March 9. The duration of Saros series 13 was 1514.5 years, and it contained 85 solar eclipses.

The Saros number of the lunar eclipse series which began on -2313 May 20 and ended on -1015 July 6. The duration of Saros series 13 was 1298.1 years, and it contained 73 lunar eclipses.

The 13th moon of Jupiter is Elara.

The known universe is currently thought to be about 13.7 billion years old, with an error of about one percent.

There are 13 zodiac constellations, which consist of the 12 signs in the astrological zodiac and Ophiuchus.

In religion

The number of participants at the Last Supper
Counting both Judas and Matthias, there were thirteen apostles
Thirteen was once associated with the Epiphany by Christians, the child Jesus having received the Magi on his thirteenth day of life.
In Judaism, 13 signifies the age of maturity (bar mitzvah) for boys
The number of principles of Jewish faith according to Maimonides
According to the Torah, God has 13 Attributes of Mercy
In modern day Wicca, thirteen is considered the maximum size of a coven, and in some traditions is the ideal number of members. There are also 13 goals of a witch

As lucky, unlucky, or significant number

See also: Triskaidekaphobia Thirteen is regarded as an unlucky number in many cultures. One (probably unverifiable) hypothesis holds that 13 is a reflection of the human fear of the unknown, since it is the first number that cannot be enumerated using our 10 fingers and 2 feet. Unreasoned fear of the number 13 is termed triskaidekaphobia. Due to this fear, some tall buildings have resorted to skipping the "thirteenth floor", either by numbering it "14" (though it's really still the thirteenth floor) or by designating the floor as "12a" or something similar. Similarly, some streets do not contain a house number 13. The thirteenth of a month is likewise ominous, particularly when it falls on a Friday (see Friday the 13th), a Tuesday in the Greek and Spanish-speaking world, or a Monday in Russia. Months with a Friday the 13th always begin on a Sunday.

According to another interpretation, the number 13 is unlucky because it is the number of full moons in a year. Women living in a natural environment tend to have their period during a full moon. A woman typically has 13 periods in a year. In the past, a woman who "bled" during a full moon was seen as a witch. The fear of women's connection to the moon, as well as the association of the full moon with mental disorders has, according to this theory, caused the number to be seen as bad luck, and connected to supernatural forces.

A small minority of left handers consider 13 to be their "lucky" number. This is possibly derived from "unlucky" being an antonym for "lucky". Since many left handers are taught to do the opposite when learning new skills from a right handed instructor, they consider 13 to be their "lucky" number as it is the opposite of 13 being the "unlucky" number.

The number is also considered unlucky by some as it is the sum of 1+4+5+3, the year of the fall of Constantinople to the Turks, marking the end of the Byzantine Empire, though it may be considered lucky by Turks on the same basis.

Amongst some Chinese people, it is regarded as a lucky number because it sounds similar to "實生", which means "must be alive". But this belief is not universal, or even known to all Chinese. Also, 13 is regarded as unlucky by those Chinese under the influence of foreign cultures.

In the Persian culture, 13 is also considered an unlucky number. On the 13th day of the Persian new year (Norouz), people consider staying at home unlucky, and go outside for a picnic in order to ward off the bad luck.

Modern-day witches have reclaimed the number 13 as a lucky and significant number. This may be similar to witches reclaiming other previously negative terms and ideas associated with witchcraft, such as black cats, brooms, and even the term witch itself.

In the Sikh religion, the number 13 is considered a special number since 13 is tera in Punjabi, which also means "yours" (as in, "I am yours, O Lord"). When Guru Nanak Dev Ji had a job of counting stocks of items, he counted from 1 to 13 (in Punjabi) as one does normally, but after reaching the count of 13, he would just repeat "tera", since all items were in fact God's, as God created them. When somebody heard this while passing, Guru Nanak Dev Ji was confronted about this, and his records were checked. It was a miracle since they were all perfect, yet he never seemed to count the items properly.

In The Hitchhiker's Guide to the Galaxy, "What is six times nine" is posed as the question to the answer to life, the universe and everything (42). This is true in base 13, although this was merely coincidence according to author Douglas Adams. Similarly, the fact that the official numbering system for counties of Norway skips over "county number 13" is due not to superstition but historical accident.

Legendary NBA superstar Wilt Chamberlain wore the number 13 on his jersey throughout his career. It signified that the number 13 was not unlucky for him, but unlucky for his opponents. Another legendary athlete who wore the number 13 was Dan Marino, who passed for more yards than any other quarterback in NFL history.

In Asian cultures, the numbers '4' and '9' are often considered unlucky due to their resemblance to the words for 'death' and 'suffering'. But if these numbers are added together, they equal the traditionally unlucky number of the West, '13'.

In mythology

The number of circles, or "nodes", that make up Metatron's Cube.
The number of gods (there were 12) at a banquet that was crashed by the evil spirit Loki (making 13) who killed one of the guests with a poison arrow.

In media

13 is a 1999 album by British band Blur
13 is a 2005 album by American band Six Feet Under
13th Floor Elevators, a Texan psychedelic band.
13 Engines, a Canadian alternative rock band.
John Mayer's album Room for Squares does not contain a track 13. Instead track 13 is one second of silence before skipping directly to track 14.
"Thirteen Ways of Looking at a Blackbird," poem by Wallace Stevens.
In the title of the movies:
- Thirteen, a 2003 movie by Catherine Hardwicke;
- Thirteen Days, a 2000 movie about the Cuban Missile Crisis;
- The Thirteenth Floor a 1999 movie;
- 13 Going on 30, a movie starring Jennifer Garner in which the protagonist is 13 years old at the outset;
- Apollo 13, a movie starring Tom Hanks (13th Apollo mission);
- Thir13en Ghosts, a 2001 horror movie starring Tony Shalhoub (a remake of 1960's 13 Ghosts, which starred Charles Herbert);
- 13 Conversations About One Thing, starring Matthew McConaughey;
- Assault on Precinct 13 (1976 movie), an action movie starring Austin Stoker and Darwin Joston;
- Assault on Precinct 13 (2005 movie), a loose remake of the 1976 movie, starring Ethan Hawke and Laurence Fishburne
- Dementia 13, a horror movie directed by Francis Ford Coppola; and
- Ward 13, an animated short movie,
- Friday the 13th, a series of movies dating from 1980 to 2003 starring a camp counselor killer and her masked killer son.
- ''Nightmare on the 13th Floor, a 1990 horror movie in which the members of a satanic cult are sacrificing people on the hidden 13th floor of a hotel.
Golgo 13, an anime about a powerful hitman. The name comes from Golgotha, the site of Jesus's crucifixion.

Strauss and Howe named Generation X the "Thirteenth Generation".
In the episode of King of the Hill when Connie has her first period and she goes with Hank to the Megalomart to buy tampons, the feminine hygiene items are in Aisle 13. This was changed to Aisle 8A when the episode reran.
A song by the band Osker, also the title of a song by the band Bigwig
Every book in A Series of Unfortunate Events has 13 chapters, and it has been reported that there will be 13 books in the series when it is finished.
The 13 Ghosts of Scooby Doo, an animated TV series where the venerable cartoon dog finds and opens a chest containing 13 of the most powerful ghouls in the world, and is charged with putting them back.
XIII, a French comic book about an assassin.
- XIII, a video game based on the aforementioned comic book.
Organization XIII, an organization of 13 non-existent beings dubbed "Nobodies" who star in the game Kingdom Hearts 2.

In fiction

The number of Stepchildren in the Noon Universe created by Arkady and Boris Strugatsky
The number of apostles who divided Earth into Stark and Arcadia in the alternate universe of The Longest Journey as well as the time, in millennia, that the Balance between the twin worlds was projected to last.

United States of America

The number of original colonies the United States was founded from. The original flag had thirteen stars, one for each state. New stars have since been added whenever a new state joins the union, but the idea of adding stripes for new states was soon dropped, so the American flag to this day has thirteen horizontal stripes, six white ones and seven red ones.
The Great Seal of the United States has:
- 13 levels of the truncated pyramid,
- 13 letters in "E Pluribus Unum", which appears in the banner running through the eagle's beak on the right side of the bill's reverse.
- 13 letters in the phrase "Annuit Coeptis", which appears over the pyramid on the left side of the bill's reverse.
- 13 stars above the Eagle,
- 13 leaves on the olive branch,
- 13 olives on the olive branch,
- 13 arrows held by the Eagle, and
- 13 bars on the shield.
The number of guns in a gun salute to U.S. Army, Air Force and Marine Corps Major Generals, and Navy and Coast Guard Rear Admirals Upper Half.
The Naval Jack of the United States has 13 stripes, 7 red and 6 white, the rattlesnake has 13 buttons on its rattle, and the motto "Don't Tread on Me" has 13 letters

In other fields

The original number of members of The Thirteen Club.
The number of loaves in a "baker's dozen"
The expression, "A year and a day" refers to 13 28-day lunar months plus 1 day
The number of Popes named Innocent, for which an honor society containing 13 members at the University of Nebraska is named ("The Society of Innocents")
The number of cards in a single suit of a standard deck of playing cards
The ASCII and Unicode value for carriage return
"Unlucky for some", according to bingo callers
The number of players in a rugby league team
The number of Plutonium slugs in Fat Man, the atomic bomb dropped on Nagasaki
The number on a Hell's Angel's patch or tattoo that refers to the thirteenth letter of the alphabet, M, for "marijuana"
13, or "X3", is the number of the Mexican street gang Sureños. It refers to the thirteenth letter of the alphabet, M, for Mexico
In rugby union one of the centres, most often but not always the outside centre, wears the 13 shirt
Israel Naval covert unit - Shayetet 13
Former professional wrestler Tazz used the number 13 in his ring gear, merchandise, and Titantron video, signifying the 13 years he wrestled in the independent circuit and ECW before being signed by WWE
A card game very similar to Tien len.
The ancient card game 'Boumpha' has 13 different cards
In tarot, card no. 13 is "the Death"

Historical years

A.D. 13, 13 B.C., 1913, 2013, etc.

Integers | Superstitions

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