6 (number)


Cardinal	6 six
Ordinal	6th sixth
Numeral system	senary
Factorization	$2 \cdot 3$
Divisors	1, 2, 3, 6
Roman numeral	VI
Unicode representation of Roman numeral	Ⅵ, ⅵ
prefixes	hexa-/hex- (from Greek)
Binary	110
Octal	6
Duodecimal	6
Hexadecimal	6
Hebrew	ו (Vav)

6 (six) is the natural number following 5 and preceding 7.

The SI prefix for 1000⁶ is exa (E), and for its reciprocal atto (a).

In mathematics

Six is the second smallest composite number, its proper divisors being 1, 2 and 3. Since six equals the sum of these proper divisors, six is a perfect number. As a perfect number, 6 is related to the Mersenne prime 3, since 2¹(2² - 1) = 6. The next perfect number is 28. Six is also a unitary perfect number, a harmonic divisor number and a highly composite number. The next highly composite number is 12.

The smallest non-abelian group is the symmetric group S₃ which has 3! = 6 elements.

S₆, with 720 elements, is the only finite symmetric group which has an outer automorphism. This automorphism allows us to construct a number of exceptional mathematical objects such as the S(5,6,12) Steiner system, the projective plane of order 4 and the Hoffman-Singleton graph. A closely related result is the following theorem: 6 is the only natural number n for which there is a construction of n isomorphic objects on an n-set A, invariant under all permutations of A, but not naturally in 1-1 correspondence with the elements of A. This can also be expressed category theoretically: consider the category whose objects are the n element sets and whose arrows are the bijections between the sets. This category has a non-trivial functor to itself only for n=6.

Six similar coins can be arranged around a central coin of the same radius so that each coin makes contact with the central one (and touches both its neighbors without a gap), but seven cannot be so arranged. This makes 6 the answer to the two-dimensional kissing number problem. The densest sphere packing of the plane is obtained by extending this pattern to the hexagonal lattice in which each circle touches just six others.

In binary code, six is 0110; in ternary code six is 20; in quaternary numeral system code six is 12; in quinary six is 11; in senary six is 10; in septenary code and all codes above (such as octal, decimal and hexadecimal) six is 6. Since it is divisible by the sum of its digits in all these bases, 6 is one of the four all-Harshad numbers.

A six-sided polygon is a hexagon. Figurate numbers representing hexagons (including six) are called hexagonal numbers. Six is also an octahedral number. It is a triangular number and so is its square (36).

In base 10, 6 is a 1-automorphic number.

The Arabic glyph

The evolution of our modern glyph for 6 appears rather simple when compared with that for the other numerals. Our modern 6 can be traced back to the Brahmin Indians, who wrote it in one stroke like a cursive lowercase e rotated 45 degrees clockwise. Gradually, the upper part of the stroke (above the central squiggle) became more curved, while the lower part of the stroke (below the central squiggle) became straighter. The Ghubar Arabs dropped the part of the stroke below the squiggle. From there, the European evolution to our modern 6 was very straightforward, aside from a flirtation with a glyph that looked more like an uppercase G.

On the seven-segment displays of calculators and watches, 6 is usually written with six segments. Some historical calculator models use just five segments for the 6, by omitting the top horizontal bar. This glyph variant has not caught on. For calculators that can display results in hexadecimal, a 6 that looks like a B is not practical.

In science

The atomic number of carbon
The number of carbon atoms and carbon-carbon bonds in benzene
The number of known quarks
The number of tastes in traditional Indian Medicine called Ayurveda. They are: sweet, sour, salty, bitter, pungent, and astringent. These tastes are used to suggest a diet based on the symptoms of the body

Astronomy

The number of colors in the rainbow (red, orange, yellow, green, blue, violet)
Messier object M6, a magnitude 4.5 open cluster in the constellation Scorpius, also known as the Butterfly Cluster

The New General Catalogue object NGC 6, a spiral galaxy in the constellation Andromeda

The Saros number of the solar eclipse series which began on -2691 March 16 and ended on -1393 May 3. The duration of Saros series 6 was 1298.1 years, and it contained 73 solar eclipses

The Saros number of the lunar eclipse series which began on -2642 July 25 and ended on -1091 February 10. The duration of Saros series 6 was 1550.6 years, and it contained 87 lunar eclipses

In religion

The number of points on a Star of David
The number of orders of the Mishnah
The number of symbolic foods placed on the Passover Seder Plate
The Jewish holiday of Shavuot starts on the sixth day of the Hebrew month of Sivan

In music

The number of strings on a standard guitar
The number of basic holes or keys on most woodwind instruments (e.g., pennywhistle, clarinet, saxophone, bassoon). These holes or keys are usually not given numbers or letters in the fingering charts
"Six geese a-laying" were given as a present on the sixth day in the popular Christmas carol, "The Twelve Days of Christmas"
The number of completed symphonies by Peter Tchaikovsky and Bohuslav Martinů
The number of Brandenburg Concertos of Johann Sebastian Bach
The concerti grossi Opus 3, organ concertos Opus 4 and Opus 7 (each) by Georg Frideric Handel
The number of string quartets of Béla Bartók
The name of the second album by Mansun released in 1998. It takes its name in part from the main character in the television series The Prisoner, and from A. A. Milne's poetry book, Now We Are Six

In sports

In American Football, the number of points received for a touchdown
In rugby union, the position of blindside flanker
In football, the number of Arsenal's legendary centre back and captain Tony Adams, both player and number are now retired
In baseball, six represents the shortstop's position
In Australian Rules football, six points are received for a goal
In cricket, a "six" or "sixer" is a shot in which the ball clears the boundary without bouncing, scoring six runs. Also, there are six balls to an over in cricket. See cricket terminology
Retired number of former baseball players Stan Musial and Al Kaline

In technology

On most phones, the 6 key is associated with the letters M, N, and O, but on the BlackBerry it is the key for J and K
The "six meter band" in amateur radio includes the frequencies from 50 to 54 MHz

In television

The audio component of any broadcast channel 6 is located at 87.7 MHz. This means that people can listen to TV stations such as WSYX using an FM radio when a television is not nearby
Number Six was the main character in the television series The Prisoner
Number Six is a character in the television mini-series and series Battlestar Galactica (2003)
Six is the name of a character on Blossom

In other fields

In the ancient Roman calendar, Sextilis was the sixth month. After the Julian reform, June became the sixth month and Sextilis was renamed August
Whether Thursday or Friday or Saturday is the sixth day of the week varies across cultures
Sextidi was the sixth day of the decade in the French Revolutionary calendar
The standard term in office for a United States senator is six years
Mark Martin's NASCAR racing number. 6 was also the number of David Pearson's car when he won his Nextel Cup Series Championship in 1966
The name of the smallest group of Cub Scouts, traditionally consisting of six people and is led by a 'sixer'. Logically speaking, this isn't always the case, particularly in packs with less than 6 Cub Scouts in it
The number of cans of soda or beer in a six-pack
The number of feet below ground level a coffin is traditionally buried; thus, the phrase "six feet under" means that a person (or thing, or concept) is dead
The number of inhabited continents, and the total number of continents if Eurasia (Europe plus Asia) is considered a single continent
The number of large geyser fields in the world
In Astrology, Virgo is the 6th astrological sign of the Zodiac
The first number when counting on your fingers requires two hands
The number of sides on a cube, hence the highest number on a standard die
The highest number on one end of a standard domino
Les Six were a group of Lost Generation writers
One of A. A. Milne's poetry books was entitled Now We Are Six
Extra-sensory perception is sometimes called the "sixth sense"
Bands with the number six in their name include Eve 6, Sixpence None the Richer, Los Xey (sei is Basque for "six")and Electric Six
Six Cardinal Directions : north, south, east, west, heaven, and land
The Six Dynasties form part of Chinese history
The Bionic Six are the heroes of an animated series
The Birmingham Six were held in prison for 16 years
Six Degrees of Kevin Bacon is a game that can be played with the names of actors and actresses
John L. Holland's RIASEC is a system that places occupations into six categories
666 is considered the Number of the Beast
There are 6 balls to an Over in Cricket
In tarot, card No. 6 is "the Lovers".

Hexa is Greek for "six". Thus:

A hexahedron is a polyhedron with six faces, with a cube being a special case
An hexagon is a regular polygon with six sides
- L' Hexagone is a French nickname for the continental part of France
A hexapod is an animal with six legs; this includes all insects
Hexameter is a poetic form consisting of six feet per line
"Hexadecimal" combines hexa- with the Latinate decimal to name a number base of 16

The prefix "hexa-" also occurs in the systematic name of many chemical compounds, such as "hexamethyl"

Sex- is a Latin prefix meaning "six". Thus:

A group of six musicians is called a sextet
Six babies delivered in one birth are sextuplets. The first set of sextuplets of whom all six survived are the Dilley sextuplets
People with sexdactyly have six fingers on each hand
The measuring instrument called a sextant got its name because its shape forms one sixth of a whole circle
The ordinal adjective senary

Historical years

A.D. 6, 6 B.C., 1906, 2006, etc.

References

The Odd Number 6, JA Todd, Math. Proc. Camb. Phil. Soc. 41 (1945) 66--68
A Property of the Number Six, Chapter 6, P Cameron, JH v. Lint, Designs, Graphs, Codes and their Links ISBN 0521423856
Some Thoughts on the Number Six, John Baez

Integers

6 (عدد) | 6 | Sis | 6 (tal) | Sechs | Seis | Ses | Sei | 6 (nombre) | 6 | 6 | Sei | 6 (מספר) | Sex | 6 (skaičius) | Chicuace | 6 (getal) | 6 | Seie | 6 (tall) | Talet 6 | 6 (liczba) | Seis | 6 (число) | Six | 6 (število) | 6 (luku) | 6 (tal) | 6 (bilang) | 6 | 6 (sayı) | 6

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