47 (number)

← 46 47 48 →
← 40 41 42 43 44 45 46 47 48 49 → List of numbers Integers ← 0 10 20 30 40 50 60 70 80 90 →
Cardinal	forty-seven
Ordinal	th
Factorization	prime
Divisors	1, 47
Greek numeral	ΜΖ´
Roman numeral	XLVII
Binary	1011112
Ternary	12023
Senary	1156
Octal	578
Duodecimal	3B12
Hexadecimal	2F16

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

In mathematics

Forty-seven is the fifteenth prime number, a safe prime, the thirteenth supersingular prime, and the sixth Lucas prime. Forty-seven is a highly cototient number. It is an Eisenstein prime with no imaginary part and real part of the form $3n-1$.

It is a Lucas number.

It is also a Keith number, because it recurs in a Fibonacci-like sequence that begins 2, 1, 3, 4, 7, 11, 18, 29, 47…. Notice that its digits appear as successive terms in the series.

Forty-seven is a strictly non-palindromic number.

Its representation in binary being 00101111, 47 is a prime Thabit number, and as such is related to the pair of amicable numbers {17296, 18416}.

Forty-seven is a Carol number. It is a real prime number.

In science

• The atomic number of silver is 47.

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 in April of 1306 BC and ended in May of 26 BC. 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 in July of 1275 BC and ended in February AD 258. The duration of Saros series 47 was 1537.5 years, and it contained 86 lunar eclipses.

As an in-joke

Forty-seven has been the favorite number of Pomona College, California, USA, since 1964. A mathematical proof, written in 1964 by Professor Donald Bentley, supposedly demonstrates that all numbers are equal to 47. However, Bentley offered it as a "joke proof" to further a popular student research project that listed real and imaginative "47 sightings". Bentley used the invalid proof to introduce his students to the concept of mathematical proofs.

Joe Menosky graduated from Pomona College in 1979 and went on to become one of the story writers of Star Trek: The Next Generation. Menosky "infected" other Star Trek writers with an enthusiasm for the number 47. As a result, 47, its reverse 74, its multiples, or combinations of 47 occur surreptitiously in almost every episode of the program and its spin-offs Star Trek: Deep Space Nine, Star Trek: Voyager and Star Trek: Enterprise. Forty-seven might be mentioned in dialogue or appear on a computer screen, for example:

• In Star Trek: Generations, Scotty manages to beam up only 47 El-Aurians before their ship is destroyed by the energy ribbon.
• In the TNG episode "Darmok," the computer of the Enterprise reports to have found 47 occurrences of the word "Darmok" in its database.
• In the DS9 episode "Whispers," the planet Parada 4 has seven moons.
• In the Voyager episode "Tattoo," we learn that the Emergency Medical Holographic Channel is 47.
• 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.
• In the 2009 film Star Trek, the Enterprise was built in Sector 47 of the Riverside Shipyards, and 47 Klingon ships are said to have been destroyed by Nero's ship, the Narada.

In pop culture

The 47 society is an outgrowth of the "movement" started at Pomona College. They explore the belief that 47 occurs in nature more frequently than other numbers and share their personal sightings in consideration of 47 being "the quintessential random number".

The tale of the Forty-seven Ronin is an historical Japanese story, based upon actual events that took place in year 1701 of the Western calendar. It is mentioned in John Frankenheimer's movie Ronin.

In the 2001 TV series Alias, the number 47 bears a specific significance concerning the Milo Rambaldi mythology. Among other things, page 47 of the Rambaldi manuscript contains the prophecy regarding the Chosen one and the Passenger. The number also often appears in different places through the series, for example in keycodes, safe-deposit boxes, hotel rooms or the number of victims in different attacks or accidents. It also appears as the same way in the 2008 TV series Fringe, which has the same creator as Alias.

The number 47 also appears in music. 47 is the number of miles of barbed wire walked by the singer of Bo Diddley's "Who Do You Love". 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 repeats, "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?" Leslie Sarony published his song "Forty-Seven Ginger-Headed Sailors" in 1928. Forty-seven is the usual number strings of a pedal harp. 47 is a song by Sunny Day Real Estate. Object 47 (named as the 47th release in the discography) is the name of an album release from Wire.

In video games, the main character of the Hitman series is known only by the name Agent 47. In Half-Life 2: Episode One, the protagonist, Gordon Freeman, begins the game with 47 points of health. In Star Wars: KOTOR you can enlist a rogue assassin droid named HK-47.

In National Treasure: Book of Secrets, the President asks Ben Gates to let him know what is on "page 47" of "the presidents book of secrets", which contains the national secrets of the U.S. presidents.

47 appears on the top of the police van in the Nicolas Cage film, Snake Eyes.

'47' is the fourth track on New Found Glory's 2009 album, Not Without a Fight. The song features the chorus: "I called you 46 times, and you answered on the 47th."

G4 software developement team often take a break at 15:47.

47 is the total numbers of balloons that a player can collect in Rareware's Nintendo 64 game Diddy Kong Racing.

Other appearances

Forty-seven is the number of Ray Garraty, the main character in The Long Walk by Stephen King. In the animated web series Afterworld, the worldwide EMP re-occurs every 47 minutes. The number 47 appears on every bottle produced by Full Sail Brewery of Hood River, Oregon. This was representative of the number of employees at one time, and CEO Irene Firmat was apparently amused that it was 47, supposedly the most common random number. The brewery now has more employees, but the number remains on the bottles. In the Japanese Anime "Claymore", the main character, Clare, is the 47th claymore.

Calendar years

• 47 BC
• A.D. 47

Other

• Telephone dialing country code for Norway
• The AK-47, also known as a Kalashnikov rifle, is one of the most widely-used military weapons in the world.
• 47 is the number of the French department Lot-et-Garonne
• The tropics of Cancer and Capricorn are located 47 degrees apart.
• The P-47 Thunderbolt was a fighter plane in WWII

External links

• Frequently Asked Questions about 47 and The 47 Society
• Pomona College's Star Trek Connection
• Star Trek Voyager and the Number 47 - Featurette, an impressive video montage, very thorough
• 47 Movies
• 47 in the Alias fandom (from the All Alias Guide)