51 (number)

51 (fifty-one) is the natural number 51 following 50 and preceding 52.

In mathematics

Fifty-one is the 14th discrete biprime and the 5th in the {3.q} semiprime family having the prime factors (3.17). Fifty-one is a pentagonal number as well as a centered pentagonal number (one of the few numbers to be both) and an 18-gonal number and a Perrin number. It is also the 6th Motzkin number, telling the number of ways to draw non-intersecting chords between any six points on a circle's boundary, no matter where the points may be located on the boundary. The aliquot sum of 51 is 21 itself a discrete biprime. 51 is the 4th member of the 11-aliquot tree with the sequence(51,21,11,1,0)

In science

• The atomic number of antimony.

Astronomy

• Messier object M51, a magnitude 8.0 spiral galaxy in the constellation Canes Venatici, also known as the Whirlpool Galaxy
• The New General Catalogue object NGC 51, a spiral galaxy in the constellation Andromeda
• The Saros number of the solar eclipse series which began on -1407 September 2 and ended on 108 February 29. The duration of Saros series 51 was 1514.5 years, and it contained 85 solar eclipses. The Saros number of the lunar eclipse series which began on -1105 June 13 and ended on 211 August 12. The duration of Saros series 51 was 1316.2 years, and it contained 74 lunar eclipses.

In sports

• Las Vegas 51s, a minor league baseball team of the Pacific Coast League
• The jersey number of American football Hall of Famer Dick Butkus, linebacker for the Chicago Bears who retired his jersey number in 1994
• The jersey number of Michael Ruffin, NBA player for the Washington Wizards
• The trademark car number of racing driver Greg Murphy
• The jersey number of Bernie Williams, MLB player for the New York Yankees
• Former jersey number of Randy Johnson, MLB pitcher while he was with the Seattle Mariners and Arizona Diamondbacks. When he was acquired by the Yankees, he began to use the number 41, since 51 was already taken by Bernie Williams
• St. Louis Cardinal Willie McGee wore #51

In other fields

Area 51

Fifty-one is:

• The first Citrus Baer number, such that all of its factors are divisors of its square.
• The code for international direct dial phone calls to Peru
• The model number of the P-51 Mustang WWII fighter aircraft
• Area 51, a parcel of U.S. military-controlled land in southern Nevada, apparently containing a secret aircraft testing facility
• Part of the title of a collection of stories by Lord Dunsany, Fifty-One Tales
• The number of the fire station and rescue engine in the TV series Emergency!
• The number of Rowdy Burns's car (Michael Rooker), later Cole Trickle's (Tom Cruise) number in the film Days of Thunder
• Washington D.C. and Puerto Rico often mentioned as the future "51st State"
• Owning 51% of stocks makes one a major shareholder
• Samuel L. Jackson starred in "Formula 51” "a.k.a. “51st State"
• "Paul is Live" album (1993): Paul McCartney's cover shot in front of London's Abbey Road Studios. A parody of the original Abbey Road. Paul, then 51, is wearing shoes, and the Volkswagen bears a license plate that reads "51 IS" (instead of "28 IF" as on Abbey Road).
• "51st anniversary" song by Jimi Hendrix
• "Come in Number 51, Your Time is Up" song by Pink Floyd
• Bob Dylan: Highway 51 Blues and the name of a band
• The Parker 51, introduced in 1941, may well be the most famous fountain pen ever made
• A brand of pastis (anise liqueur) manufactured by Pernod Ricard
• "Cachaça 51" is the brand name of a cachaça produced by a Companhia Müller de Bebidas in Pirassununga, São Paulo, Brasil.
• Video games Designer Goichi Suda uses 51 in his nickname (Suda51) as a play on words with his name (Goichi, GO translates to 5, and ICHI to 1)

Historical years

51 A.D., 51 B.C., 1951, 2051, etc.