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.
- 47 is the atomic number of silver.
- 47 is the atomic mass of one of the naturally occurring stable isotopes of titanium.
- The 47-year cycle of Mars: after 47 years - 22 synodic periods of 780 days each - Mars returns to the same position among the stars and is in the same relationship to the Earth and Sun. The ancient Mesopotamians discovered this cycle.
- 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 1306 BC and ended in May 26 BC. The duration of solar 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 1275 BC and ended in February AD 258. The duration of lunar Saros series 47 was 1537.5 years, and it contained 86 lunar eclipses.
In popular culture
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. The proof used limits to show that the sum of the two equal sides of an isosceles triangle is equal to the base side. Bentley chose forty-seven as the base side, but he could have used any number.
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 in a large number of episodes of the program and its spin-offs Star Trek: Deep Space Nine, Star Trek: Voyager and Star Trek: Enterprise, usually in the form of dialogue or on-screen labels or computer screens. For example:
- In the TNG episode "Darmok", the computer of the Enterprise reports to have found 47 occurrences of the word "Darmok" in its database.
- In Star Trek Generations, Scotty manages to beam up only 47 El-Aurians before their ship is destroyed by the energy ribbon.
- In the Voyager episode "Parallax", we learn that the Emergency Medical Holographic Channel is 47 and that the EMH has the experience of 47 individual medical officers.
- 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.
J. J. Abrams, who produced and directed Star Trek, frequently uses the number 47 in his productions, including episodes of his TV series Fringe. In the Season 1 episode "Bad Dreams", aired shortly before the release of Star Trek in theaters, Nick Lane's bulletin board features a large centrally-located sheet of paper with only the number 47 in huge typeface. It recurs in the series: for example, 47 minutes being the maximum amount of time for a time chamber in the series to last, and there being exactly 47 shapeshifters. J.J. Abrams continues to incorporate 47 into movies and series he produces and directs. There are many 47's in Fringe, Alias, and Revolution. In Star Wars: The Force Awakens, the thermal oscillator is located in Precinct 47. In the Season 1 episode "Soul Train" of the series Revolution, the characters are involved with an old train engine where the engine number happens to be 47.
2012 U.S. Presidential Election
During the 2012 election, Republican candidate Mitt Romney made a comment claiming that 47 percent of Americans do not pay any income tax. Since the comment potentially sabotaged his chances of winning the election against Barack Obama, the term "47 percent" has been used by critics to describe actions that could potentially damage a political candidate. For example, during the 2016 election, Hillary Clinton's speech labeling half Donald Trump's supporters as "deplorable" was compared by critics to Romney's 47 percent speech.
The Brooklyn-based hip hop collective Pro Era and its late co-founder Jamal Dewar, better known by his stage name Capital STEEZ, have made references to the number 47 in various songs by members of the group. While in the middle of the production of his debut mixtape AmeriKKKan Korruption, Capital STEEZ was fixiated with the number; he felt that 47 was a perfect expression of balance in the world, representing the tension between the heart and the brain, the fourth and seventh chakra, respectively.
The design of one of Pro Era's logos is the number 47 with its digits joined together. It has sparked controversy due to its similarity to the Nazi flag. Like the Nazi flag, the logo has a red field with a solid white circle and a black insignia. Instead of a swastika, the circular white field of the sticker contains the 47 symbol, which bears close resemblance to the swastika and to a wolfsangel, both of which are associated with Nazism and Neo-Nazism. Stickers of the logo and graffiti of the symbol appeared in numerous locations around Edward R. Murrow High School and the Brooklyn neighborhood of Midwood (where the school is located) in March 2014, being planted by members of Pro Era to honor the memory of Capital STEEZ. According to local news station News 12 Brooklyn, the group has explained that the logo was designed the way it was to draw attention, and that the symbol resembles peace, love and balance, as with the swastika's significance in various religions. They say that it is supposed to be a spiritual symbol and not an offensive one. Capital STEEZ also believed that the logo's resembelence of a swastika is a commentary on the appropriation of what was originally a peaceful & spiritual symbol with roots in Eastern religions.
On the night of December 23, 2012, Capital STEEZ posted a tweet at 11:59 PM simply saying, "The end." He would then take his own life by jumping off the rooftop of the Cinematic Music Group headquarters in Manhattan’s Flatiron District. It’s worth noting that the numbers in the date—12/23/12—add up to 47, though it may be coincidental.
- 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.
- The CH-47 Chinook, a helicopter.
- 47 is the number of the French department Lot-et-Garonne.
- The Tropic of Cancer and the Tropic of Capricorn are located 47 degrees apart.
- The P-47 Thunderbolt was a fighter plane in World War II.
- 47 is the name of the agent in the Hitman video game series.
- There are Forty-seven Ronin in the famous Japanese story.
- There are 47 Prefectures of Japan.
- "Sloane's A005385 : Safe primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
- "Sloane's A002267 : The 15 supersingular primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
- "Sloane's A005479 : Prime Lucas numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
- "Sloane's A100827 : Highly cototient numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
- "Sloane's A007629 : Repfigit (REPetitive FIbonacci-like diGIT) numbers (or Keith numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
- "Sloane's A016038 : Strictly non-palindromic numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
- "Sloane's A093112 : a(n) = (2^n-1)^2 - 2". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
- The NGC / IC Project - Home of the Historically Corrected New General Catalogue (HCNGC) since 1993
- Internet Archive Wayback Machine
- NASA - Lunar Eclipses of Saros Series 1 to 175
- "The Mystique of 47". Pomona College (via Internet Archive). Archived from the original on 2006-09-01. Retrieved 2010-05-16.
- "The Mystery of 47". Pomona College. Retrieved 2007-08-29.
- "Stardate 47". Pomona College (via Internet Archive). Archived from the original on September 1, 2006. Retrieved 2010-05-17.
- "Starbase Pomona". Pomona College (via Internet Archive). Archived from the original on September 1, 2006. Retrieved 2010-05-17.
- schlock.net: A letter from Brannon Braga
- Roco. "Revolution Observations: 1.05 Soul Train". Seriable.com. Retrieved 28 April 2013.
- Dixon, Kim (October 19, 2012). "Analysis: "47 percent" lament belies Republican tax credit support". Reuters. Retrieved September 11, 2016.
- Cillizza, Chris (March 4, 2013). "Why Mitt Romney's "47 percent" comment was so bad". Washington Post. Retrieved September 11, 2016.
- Chozick, Amy (September 10, 2016). "Hillary Clinton Calls Many Trump Backers 'Deplorables,' and G.O.P. Pounces". The New York Times. Retrieved September 11, 2016.
- Blake, Aaron (September 10, 2016). "Did Hillary Clinton just make her own '47 percent' gaffe?". Washington Post. Retrieved September 11, 2016.
- Mehta, Seema (September 10, 2016). "Campaign 2016 updates: Republicans pounce upon Clinton 'deplorables' remark. She apologizes. Sort of.". Los Angeles Times. Retrieved September 11, 2016.
- Rosenberg, Eli (November 26, 2013). "Capital STEEZ: King Capital". The Fader. Archived from the original on August 31, 2016. Retrieved August 30, 2016.
- "Controversial symbol shows up along Avenue K in Midwood". News 12 Brooklyn. News 12 Brooklyn. 24 March 2014. Retrieved 21 April 2014.
- "KING CAPITAL $TEEZ". Twitter.
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