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Cardinal | fifty-five | |||

Ordinal | 55th (fifty-fifth) | |||

Factorization | 5 × 11 | |||

Divisors | 1, 5, 11, 55 | |||

Greek numeral | ΝΕ´ | |||

Roman numeral | LV | |||

Binary | 110111_{2} | |||

Ternary | 2001_{3} | |||

Quaternary | 313_{4} | |||

Quinary | 210_{5} | |||

Senary | 131_{6} | |||

Octal | 67_{8} | |||

Duodecimal | 47_{12} | |||

Hexadecimal | 37_{16} | |||

Vigesimal | 2F_{20} | |||

Base 36 | 1J_{36} |

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

## Contents

## Mathematics

55 is the 10th Fibonacci number^{[1]} and a triangular number (the sum of the consecutive numbers 1 to 10).^{[2]} It is the largest Fibonacci number to also be a triangular number.

It is a square pyramidal number (the sum of the squares of the integers 1 to 5)^{[3]} as well as a heptagonal number,^{[4]} and a centered nonagonal number.^{[5]}

In base 10, it is a Kaprekar number.^{[6]}

## 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

## Music

- "Schfifty Five", a song produced by Gröûp X.
^{[7]} - 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. - "I Can't Drive 55", a song by Sammy Hagar
- "Ol' '55", a song by Tom Waits
- Ol' 55 (band), an Australian rock band.
- Primer 55 an American band
*Station 55*, an album released in 2005 by Cristian Vogel*55 Cadillac*, an album by Andrew W.K.

## Transportation

- In the United States, the National Maximum Speed Law prohibited speed limits higher than 55 miles per hour (90 km/h) from 1974 to 1987

## Film

*55 Days at Peking*a film starring Charlton Heston and David Niven

## Years

## Other uses

- Gazeta 55, an Albanian newspaper
- Agitation and Propaganda against the State, also known as Constitution law 55, a law during Communist Albania.
- The code for international direct dial phone calls to Brazil
- A 55-gallon drum; see 44 gallon drum
- Numbered car in NASCAR, currently being driven by David Ragan
- The Élysée, the official residency of the French Republic president, which address is 55 rue du Faubourg-Saint-Honoré in Paris.
- The number of the laps of the Abu Dhabi Grand Prix.

## See also

- 55th Regiment of Foot (disambiguation)
- Channel 55 (disambiguation)
- Type 55 (disambiguation)
- Class 55 (disambiguation)
- List of highways numbered 55

## References

**^**"Sloane's A000045 : Fibonacci numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Sloane's A000217 : Triangular numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Sloane's A000330 : Square pyramidal numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Sloane's A000566 : Heptagonal numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Sloane's A060544 : Centered 9-gonal (also known as nonagonal or enneagonal) numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Sloane's A006886 : Kaprekar numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Group X".*Albino Blacksheep*. Retrieved 30 July 2018.