55 (number)

← 54 55 56 →
← 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 × 11
Divisors	1, 5, 11, 55
Roman numeral	LV
Binary	1101112
Ternary	20013
Quaternary	3134
Quinary	2105
Senary	1316
Octal	678
Duodecimal	4712
Hexadecimal	3716
Vigesimal	2F20
Base 36	1J36

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

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]

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".
• 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
• Cristian Vogel released an album in 2005 with the title "Station 55"
• Ol' 55 (band), an Australian rock band.
• Primer 55 an American band
• 55 Cadillac, an album by Andrew W.K.

Transportation

• The highest speed limit allowed in the United States between 1974 and 1986 per the National Maximum Speed Law.
• Highway 55, several roads

Film

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

Years

• 55 A.D.
• 55 B.C.
• 1955

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.

See also

• 55th Regiment of Foot (disambiguation)
• Channel 55 (disambiguation)
• Type 55 (disambiguation)
• Class 55 (disambiguation)
• Highway 55

References

1. "Sloane's A000045 : Fibonacci numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
2. "Sloane's A000217 : Triangular numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
3. "Sloane's A000330 : Square pyramidal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
4. "Sloane's A000566 : Heptagonal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
5. "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.
6. "Sloane's A006886 : Kaprekar numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.