47 (number)


Cardinal	47 forty-seven
Ordinal	47th forty-seventh
Factorization	prime
Roman numeral	XLVII
Binary	0101111
Hexadecimal	2F

47 (forty-seven) is the natural number following 46 and followed by 48.

In mathematics

Forty-seven is the 15^th prime number, a safe prime, a supersingular prime, and the 6^th Lucas prime. 47 is a highly cototient number. It is an Eisenstein prime with no imaginary part and real part of the form

3n - 1

It is also a Keith number, because it recurs in a Fibonacci-like sequence started from its base 10 digits: 4, 7, 11, 18, 29, 47...

47 is a strictly non-palindromic number.

Its representation in binary being 101111, 47 is a prime Thabit number, and as such is related to the pair of amicable numbers {17296, 18416}.

47 is a Carol number.

In science

The atomic number of silver

Astronomy

Messier object M47, a magnitude 4.5 open cluster in the constellation Puppis
The New General Catalogue object NGC 47, a barred spiral galaxy in the constellation Cetus. This object is also designated as NGC 58.
The Saros number of the solar eclipse series which began on -1306 April 2 and ended on -26 May 10. The duration of Saros series 47 was 1280.1 years, and it contained 72 solar eclipses.
The Saros number of the lunar eclipse series which began on -1275 July 31 and ended on 258 February 5. The duration of Saros series 47 was 1537.5 years, and it contained 86 lunar eclipses.

References to 47

There exists a 47 society, an outgrowth of a movement started at Pomona College, California, USA, which propagates the belief (or, to some, the inside joke) that the number forty-seven occurs in nature with noticeably higher frequency than other natural numbers. The origin of 47 lore at Pomona appears to be a mathematical proof, written in 1964 by Professor Donald Bentley, which supposedly demonstrated that all numbers are equal to 47. However, the proof mentioned above was used by Professor Bentley as a "joke proof" to introduce his students to the concept of mathmatical proofs, and is not mathmatically valid.

Following on from this, Joe Menosky, who graduated from Pomona College in 1979 and went on to become one of the story writers of The Next Generation, "infected" other Star Trek writers with it, and as a result the number (or its reverse, 74) occurs in some way or other in almost every episode of this program and its spin-offs Deep Space Nine, Voyager and Enterprise. The number might be mentioned in the dialogue, it might appear on a computer screen a character is looking at, and it might be a substring of a larger number. The number also appears on some of the DVD menu screens for the episodes. They range from extremely obvious (for example, "shields are down to 47%"), to very well hidden. Some examples are listed here:

In the TNG episode "Darmok," Worf reports a particle gradient of 4/7.
In the DS9 episode "Whispers," the planet Parada IV has seven moons.
In the Voyager episode "Non Sequitur," Harry Kim lives in apartment 4-G, G being the seventh letter of the alphabet. The intentionality of this reference to 47 was confirmed by Brannon Braga, the writer of that episode ^*.

According to a joke by Rick Berman (the co-creator and executive producer of several Star Trek series), "47 is 42, corrected for inflation".

Eventually it spread outside of Star Trek; 47s have been spotted in The Simpsons, Law & Order, NYPD Blue, Threshold, Alias, Lost, Scrubs, South Park, Red Dwarf, and The West Wing.

47 also has been placed in video games in the same deliberate way for almost 20 years. Examples include Earl Weaver Baseball (the batter's uniform number is 47), Hitman (the name of the main character is Agent 47, commonly referred to as simply "47"), Knights of the Old Republic (HK-47), and Episode One (starting player health is 47).

In 1998, Japanese electronic musician Takako Minekawa released the album Cloudy Cloud Calculator, which featured a song about the number 47 entitled "Kangaroo Pocket Calculator". The song repeatedly states that "47 is a magical number. 47 plus 2 equals 49. 47 times 2 equals 94. 49 and 94. 94 and 49. Relationship between 47 and 2... is magic" and eventually concludes "Isn't it a coincidence?"

The TV show Alias likes the number 47. The number 47 has appeared in nearly every episode, from being a casino's access code, "4747," in "The Coup," to being Milo Rambaldi's favorite number, as he made Page 47 of all his manuscripts the most important.

In Lucky Number Slevin, Nick Fischer's apartment is number 47.

Group 47 was a literary association in post-WWII Germany.

In the 1976 movie The Omen, the priest that warns Robert Thorn about Damien has 47 Crosses nailed to his walls.

The Star Wars franchise references the number in the form of the T-47 Snowspeeders in The Empire Strikes Back (1980), mentioned in dialog by Luke Skywalker. In one episode of Alias' a character paraphrases the line from Empire.

In the television show Scrubs in season 4, the main character, J.D, moves out into his own apartment, whose number is 47.

In other fields

Forty-seven is also:

sometimes erroneously noted as the number of miracles performed by Jesus listed in the New Testament
the code for international direct dial phone calls to Norway
the model number of the Republic P-47 Thunderbolt WWII fighter bomber
the title of an award-winning novel by Walter Mosley
the number of the French département Lot-et-Garonne
the number of mountains in "the 47" High Peaks of the Adirondacks
the number of samurai involved in the famous historical Ako vendetta; sometimes referred to as the 47 Ronin
the number of bullets that killed Pancho Villa in 1923
the model number of the AK-47 assault rifle
the jersey number of former baseball pitching great Jack Morris
the jersey number of NBA star Andrei Kirilenko. His shoes are custom made by Nike and have "AK-47" embroidered on them.
the year AD 47, 47 BC, and 1947
"Black '47" is historically considered the worst year of the Irish Potato Famine. The phrase inspired the Irish-American rock band of the same name.
the model number of the droid character HK-47 from the video game Star Wars Knights of the Old Republic (Note: This is not a reference to the AK-47 assault rifle. See HK-47#Name for more details.)
the jersey number of former Ohio State great, and current Green Bay Packer Linebacker A.J. Hawk.
The name of Agent 47, from the Hitman video game series

External links

Frequently Asked Questions about 47 and The 47 Society
Pomona College's Star Trek Connection
The Mystique of 47 — trivia about the number 47, also part of the Pomona College website
List of 47 References at Memory Alpha — article listing occurrences of the number in episodes and movies of Star Trek, and its context within the plot
47 in the Alias fandom (from the All Alias Guide)
The 47s Community — LiveJournal community to post photos and stories about the number
Comparative frequency analysis of 42 and 47 against other numbers from Thoreaulylazy's blog

Integers | In-jokes