55 (number)

← 54 56 → 55
← 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-five
Ordinal	55th (fifty-fifth)
Factorization	$5 \cdot 11$
Divisors	1, 5, 11, 55
Roman numeral	LV
Binary	1101112
Octal	678
Duodecimal	4712
Hexadecimal	3716

55 (fifty-five) is the natural number following 54 and preceding 56.

Albania

• Gazeta 55, a newspaper
• Constitution law 55, a law during Communist Albania.

Mathematics

Fifty-five has the interesting property that it is the 10th Fibonacci number and the sum of the numbers 1 to 10.

It is a heptagonal number, a centered nonagonal number, and a triangular number (the sum of the numbers 1 to 10) and a square pyramidal number (the sum of the squares of the integers 1 to 5). It is also a Fibonacci number (the largest Fibonacci number to also be a triangular number) and a Kaprekar number.

55 is a semiprime, being the product of 5 and 11 and it is the 2nd member of the (5.q) semiprime family. 55 is one of only two integers with an aliquot sum of 17 (the other being 39). 55 has an aliquot sequence of 4 members: (55, 17, 1, 0).

Science

• The atomic number of caesium.

Astronomy

• Messier object M55, a magnitude 7.0 globular cluster in the constellation Sagittarius
• The New General Catalogue object NGC 55, a magnitude 7.9 barred spiral galaxy in the constellation Sculptor
• The Saros number of the solar eclipse series which began on -1255 July 6 and ended on 43 August. The duration of Saros series 55 was 1298.1 years, and it contained 73 solar eclipses. The Saros number of the lunar eclipse series which began on -935 April 25 and ended on 345 June. The duration of Saros series 55 was 1280.1 years, and it contained 72 lunar eclipses.

Music

• A song produced by Group X was called "Schfifty Five". With the addition of a flash animation, "Schfifty Five" became a common internet meme
• The name of a song by British Indie Rock Band Kasabian. The song was released as a B side to Club Foot and was recorded live when the band performed at London's Brixton Academy.
• Sammy Hagar sang "I Can't Drive 55"
• Tom Waits (and later Sarah McLachlan) sang "Ol' 55"
• Cristian Vogel released an album in 2005 with the title "Station 55"
• Ol' 55, an Australian rock band.
• Primer 55 an American band
• Andrew W.K. has an album called 55 Cadillac which contains the track "5" which is track five on the album, making it look like 55 in the tracklisting.

Politics

• The number of Delegates who attended the United States Constitutional Convention in 1787.
• Adolf Hitler was the fifty-fifth member of the National Socialist German Workers Party.

Geography

• The number of the French department Meuse.
• The code for international direct dial phone calls to Brazil

Measurements

• In US gallons, a standard size of drum; see 44 gallon drum

Transportation

• The highest speed limit allowed in the United States between 1974 and 1986 per the National Maximum Speed Law.
• In many states of the United States, a very common speed limit for rural secondary roads and many urban freeways.
• The number of European route E55 from Helsingborg, Sweden to Greece.
• The designation of I-55, a freeway that runs from Louisiana to Illinois.
• Year identifier used on motor vehicles registered in the UK between 1st September 2005 and 28th February 2006.

Film

• The number of Sacha Baron Cohen's character, Jean Girard, in the 2006 film Talladega Nights: The Ballad of Ricky Bobby. In real life, however, it is the number of Michael Waltrip
• 55 Days at Peking starred Charlton Heston and David Niven

Sports and games

• In sports, the jersey number "55" is also known as "Double Nickels" or "Double Nicks".
• In the dice game of craps, if you roll two 5s or a "55" this is commonly known as a hard 10 or double nickels.

Years

55 A.D., 55 B.C., 1955, 2055, etc.