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

In mathematics

Forty-seven is the 15^th prime number, a safe prime, and the 8^th Lucas number. 47 is a highly cototient number.

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, it is not palindromic in any base from base 2 to base 45.

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 Feb 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 math 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 a subtle hidden way in almost every episode of this program and its spin-offs Star Trek: Deep Space Nine and Star Trek: Voyager. 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.

According to a (joking) statement by Rick Berman (the co-creator and executive producer of several Star Trek series), "47 is 42, corrected for inflation". The number 47 is referenced often in the television series Alias. It is also the name of the main character in the video game Hitman, and appears in the name of the assassin droid HK-47 in Star Wars: Knights of the Old Republic.

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 department Lot-et-Garonne.
• the number of mountains in "the 47" peaks of the Adirondacks.
• the number of samurai involved the famous historical Ako vendetta; sometimes referred to as the 47 Ronin.
• the number of bullets that killed Pancho Villa in 1923.
• 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
• "The 47s Community" — LiveJournal community to post photos and stories about the number
• 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