|Factorization||5 × 17|
|Divisors||1, 5, 17, 85|
85 is the product of two prime numbers (5 and 17), and is therefore a biprime; specifically, the 24th biprime not counting perfect squares. Together with 86 and 87, it forms the second cluster of three consecutive biprimes. The aliquot sum of 85 is 23 within the aliquot sequence (23,1,0), 85 being the second composite number in the 23-aliquot tree.
85 can be expressed as a sum of two squares in two ways, 85= 92 + 22 = 72 + 62, the lowest number to have this property with all squares greater than 1.[not in citation given][importance?] It is also the length of the hypotenuse of four pythagorean triangles.
In base 10 it is a Smith number.
85 is 1111 (a repunit) in base 4.
- Messier object M85 is a magnitude 10.5 lenticular galaxy in the constellation Coma Berenices
- NGC 85 is a galaxy in the constellation Andromeda
- 85 Io is a large main belt asteroid
- 85 Pegasi is a multiple star system in constellation of Pegasus
- 85 Ceti is a variable star in the constellation of Cetus
- 85P/Boethin is a periodic comet
- 85 is the Saros number of the solar eclipse series which began on -170 March 14 and ended on 1110 April (1280.1 years, 72 solar eclipses)
- 85 is also the Saros number of the lunar eclipse series which began on -103 August 2 and ended on 1267 November (1370.3 years, 77 lunar eclipses)
In titles and names
- Federalist No. 85, by Alexander Hamilton, the last of The Federalist Papers (1788)
- The 85 Ways to Tie a Tie, a book by Thomas Fink and Yong Mao
- 85 Days: The Last Campaign of Robert Kennedy a book by Jules Witcover
- Live/1975–85, an album of live reordings by Bruce Springsteen (1986)
- 80–85 a compilation album by Bad Religion (1991)
- Cupid & Psyche 85, an album by band Scritti Politti (1985)
- 45/85 was a television documentary on World War II
- Minuscule 85, Papyrus 85, Lectionary 85 are early Greek manuscripts of the New Testament
- "85", a 2000 rap single by YoungBloodz, from their album Against Da Grain
- 85°C, a Taiwanese coffee store chain.
In U.S. college athletics, schools that are members of NCAA Division I are limited to providing athletic scholarships to a maximum of 85 football players in a given season. The specifics vary by the two Division I football subdivisions:
- In the top-level FBS, each player provided with a scholarship may, and almost always does, receive a full scholarship.
- In the second-level FCS, schools are allowed to provide football-related athletic aid equivalent to 63 full scholarships, but this aid may be divided among up to 85 players as the schools see fit.
In other fields
Eighty-five is also:
- The year AD 85, 85 BC, or 1985.
- The Muslim calendar year 85 AH.
- The atomic number of astatine
- The number of the French department Vendée
- The ISBN Group Identifier for books published in Brazil
- The radix of the Ascii85 (sometimes called Base85) binary-to-text encoding
- The IQ and nickname of Aaron in Alien 3
- The number worn by Chad Ochocinco, whose name means "eight five" in Spanish
- Arabigere 85 is a village in India
- E85 fuel is 85% ethanol and 15% conventional gasoline
- MCS-85 was a family of Intel processors including the 8085
- TI-85 was a graphing pocket calculator by Texas Instruments
- KC 85 was a family of small computers built in East Germany in the 1980s
- PMD 85 was a personal computer built in Czechoslovakia in 1985
- Learjet 85 is an all-composite plane being developed by Bombardier Aerospace
- British Rail Class 85, a category of UK train locomotives
- DRG Class 85, a category of German train locomotives
- TK85 was a clone of the Sinclair ZX81 made in Brazil in 1983
- Lima Site 85 was a battle in the Vietnam War
- A85 is the Dutch Defence in the Encyclopaedia of Chess
- EF 85mm is a photographic camera lens by Canon
- F-85 is a family of Oldsmobile cars
In military technology
- 85mm is a common caliber for cannons
- SU-85 was a Soviet tank
- TR-85 was a Romanian battle tank
- Tu-85 was a prototype Soviet bomber
- ASU-85 a Soviet self-propelled gun
- CZ 85 is a Czech 9mm semiautomatic pistol
- PT-85 is a Korean tank
- 7.62 Tkiv 85 is a Finnish army rifle
- HG 85 is a Swiss fragmentation grenade
- Taurus Model 85, a 9mm revolver made in Brazil
- List of highways numbered 85
- List of highways numbered 85A
- Type 85, a designation of many military equipment
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