55 (number)

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

Mathematics

55 is the 10th Fibonacci number and a triangular number (the sum of the numbers 1 to 10). 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) as well as a heptagonal number, and a centered nonagonal number.

In base 10, it is 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).

55 is also the sum of consecutive numbers from 1 to 10.

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

See also

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