85 (number)

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85 (eighty-five) is the natural number following 84 and preceding 86.

84 85 86
Cardinal eighty-five
Ordinal 85th
Factorization 5 × 17
Divisors 1, 5, 17, 85
Roman numeral LXXXV
Binary 10101012
Ternary 100113
Quaternary 11114
Quinary 3205
Senary 2216
Octal 1258
Duodecimal 7112
Hexadecimal 5516
Vigesimal 4520
Base 36 2D36

In mathematics[edit]

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 is an octahedral number, a centered triangular number, a centered square number, and a decagonal number.

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.[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.

In astronomy[edit]

In titles and names[edit]

In sports[edit]

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[edit]

Published in Brazil:
ISBN 85..

Eighty-five is also:

In military technology[edit]

  • 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

See also[edit]


  1. ^ "Sloane's A007692 ", The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.. Note that the two smaller numbers on this list, 50 and 65, have 1 as one of the squares in their representations as sums of two squares.

External links[edit]