Английская Википедия:55 (number)
Шаблон:Infobox number 55 (fifty-five) is the natural number following 54 and preceding 56.
Mathematics
55 is the fifteenth discrete semiprime,[1] and the second with 5 as the lowest non-unitary factor. Thus, of the form 5 × q with q a higher prime, in this case equal to 11.
It contains an aliquot sum of 17; the seventh prime number, within an aliquot sequence of one composite number (55, 17, 1, 0) that is rooted in the 17-aliquot tree.
55 is the tenth Fibonacci number.[2] It is the largest Fibonacci number to also be a triangular number (the tenth as well);[3] it is furthermore the fourth doubly triangular number.[4]
55 is also an early member inside other families of polygonal numbers; it is strictly (when including 0 as the zeroth indexed member) the fifth:
It is also the fourth centered nonagonal number.[5]
In decimal, 55 is a Kaprekar number,[6] whose digit sum is also 10. It is the first number to be a sum of more than one pair of numbers which mirror each other (23 + 32 and 14 + 41).
Fermat primes
The prime indices in the prime factorization of <math>55 = 5 \times 11</math> are the respectively the third and fifth, where the first two Fermat primes of the form <math>2^{2^n} + 1</math> are (3, 5).
Where 17 — the aliquot part of 55 — is the third Fermat prime, the fifty-fifth prime number 257[7] is the fourth such prime number. The base-ten digit representation of the latter satisfies a subtractive concatenation of <math>7 - 2 = 5</math>, wherein 77 is the fifty-fifth composite number.[8]Шаблон:Efn
In decimal representation, the fifth and largest known Fermat prime is 65537,[9] which contains a "55" string inside (and where as a number, 637 is the eleventh non-trivial decagonal number).[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
Music
- The name of a song by 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.
- "55", a song by Mac Miller
- "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 Шаблон:Convert 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 for containing oil, etc.
- 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)
- List of highways numbered 55
References
Шаблон:Notelist Шаблон:Reflist Шаблон:Integers
