51 (number)

← 50 52 → 51
← 50 51 52 53 54 55 56 57 58 59 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
Cardinal	fifty-one
Ordinal	51st (fifty-first)
Factorization	$3 \cdot 17$
Divisors	1, 3, 17, 51
Roman numeral	LI
Binary	110011₂
Octal	63₈
Duodecimal	43₁₂
Hexadecimal	33₁₆

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

1 In mathematics
2 In science
- 2.1 Astronomy
3 In sports
4 In other fields
5 Historical years
6 References
- 6.1 Footnotes

In mathematics

Fifty-one is the 14th discrete biprime and the 5th in the {3.q} semiprime family having the prime factors (3.17). 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).

51 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.

Since the greatest prime factor of 51² + 1 = 2602 is 1301, which is clearly more than 51 twice, 51 is a Størmer number.

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 +193 July 31. The duration of Saros series 51 was 1298.1 years, and it contained 73 lunar eclipses.

In sports

Las Vegas 51s, a minor league baseball team of the Pacific Coast League
The jersey number 51 has been retired by a number of North American sports teams in honor of past playing greats.
- In the National Football League:
  - The Carolina Panthers, for Sam Mills.
  - The Chicago Bears, for Hall of Famer Dick Butkus.
- In Major League Baseball:
  - The San Diego Padres, for Trevor Hoffman.

In other fields

Fifty-one is:

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
Washington D.C. and Puerto Rico often mentioned as the future "51st State"
"51st anniversary" song by Jimi Hendrix
"Come in Number 51, Your Time is Up" song by Pink Floyd
"Number 51" is referenced in the song "The Happening," by The Pixies
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
Pixar's film Cars tells about a rookie racecar, Lightning McQueen who crashes into Radiator Springs, a town on Highway 66. There, he meets the town's doctor & judge, Doc Hudson, a royal blue 1951 Hudson Hornet. Later, he (Doc) turns out to be a retired racecar himself. (Fabulous Hudson Hornet). As a racecar, his racing number was 51. 51 is also on Doc's licence plate (51HHMD).
"Cachaça 51" is the brand name of a cachaça produced by a Companhia Müller de Bebidas in Pirassununga, São Paulo, Brasil.
The '51 is a guitar made by Fender's second brand, Squier. It is notable for being one of only a few original models produced by the marque.
The number of the French department Marne
Suda51 is the nickname of Goichi Suda, the CEO of Grasshopper Manufacturer.
Year identifier used on motor vehicles registered in the UK between 1 September 2001 and 28 February 2002
The station number and apparatus numbers from the TV series Emergency!
51 (film)

Historical years

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