47 (number)

47 is the natural number following 46 and followed by 48.

Template:Numbers 40s
Cardinal	forty-seven
Ordinal	47th (forty-seventh)
Factorization	prime
Roman numeral	XLVII
Binary	0101111
Hexadecimal	2F

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
• In 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 humorous 47 society at Pomona College, California, USA which propagates the (joking) belief 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.

Following on from this inside joke, Joe Menosky, who graduated from Pomona College in 1979 and went on to become one of the story writers of Star Trek: The Next Generation, "infected" other Star Trek writers with it, and as a result the number occurs in some way or other in almost every episode of this program and its spin-offs Star Trek: Deep Space Nine, Star Trek: Voyager and Star Trek: 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:

• Voyager's registration number is NCC-74656, and warp factor 7 is 656 times the speed of light; substituting the 7 in for 656 would thus yield NCC-747.
• In one episode of Voyager, a character refers to an event that happened on Earth in the year 2209, which is 47 squared.
• In "Non Sequitur", an episode of that series, 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 [1].

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

In the fan realm, Section 47 is an online Star Trek RPG.

Eventually it spread outside of Star Trek; 47s have been spotted in The Simpsons, Law & Order, NYPD Blue, Alias, Lost and Scrubs (such as J.D.'s room number after he moved out in the last episode of season 4).

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) and Hitman (the name of the main character 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?"

Forty-seven is also:

• 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 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 year AD 47, 47 BC, and 1947.

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
• TV Tome Thread Number 47 — article listing occurrences of the number on the television show Alias
• 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