80 (number)

From Wikipedia, the free encyclopedia

80 (eighty) is the natural number following 79 and preceding 81.

← 80 81 82 83 84 85 86 87 88 89 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
Cardinal	80 eighty
Ordinal	80th eightieth
Factorization
Divisors	1, 2, 4, 5, 8, 10, 16, 20, 40, 80
Roman numeral	LXXX
Roman numeral (Unicode)	LXXX, lxxx
Binary	1010000
Octal	120
Duodecimal	68
Hexadecimal	50
Greek numeral	π´
Hebrew	פ (Pe)

Contents 1 In mathematics 2 In astronomy 3 In other fields 4 External links

[edit] In mathematics

The sum of Euler's totient function φ(x) over the first sixteen integers is 80.

Adding up some subsets of its divisors (e.g., 1, 4, 5, 10, 20 and 40) gives 80, hence 80 is a semiperfect number.

80 is a Harshad number number in base 10.

[edit] In astronomy

• Messier object M80, a magnitude 8.5 globular cluster in the constellation Scorpius
• The New General Catalogue object NGC 80, a magnitude 12.1 spiral galaxy in the constellation Andromeda
• The Saros number of the solar eclipse series which began on 333 BC June 13 and ended on 929 July 9. The duration of Saros series 80 was 1262.1 years, and it contained 71 solar eclipses. Further, the Saros number of the lunar eclipse series which began on 121 BC January 27 and ended on 1213 April 6. The duration of Saros series 80 was 1334.2 years, and it contained 75 lunar eclipses.

[edit] In other fields

Eighty is also:

• The atomic number of mercury
• A cross-country interstate in the United States
• the number of units in a fourscore
• the age at which one becomes an octogenarian
• in the title of Around the World in Eighty Days by Jules Verne
• the model number of the computers TRS-80, Sinclair ZX80, and Aster CT-80
• the model number of:
  • T-80, a Soviet tank
  • IAR 80, a Romanian WWII fighter aircraft
  • McDonnell Douglas MD-80, Arado Ar 80, and F-80 Shooting Star
• part of the name of the bands Eighty-D, Eighty Proof Soul and Element Eighty
• the upper age limit for cardinals to vote in papal elections
• the percentage of consequences that stem from 20% of the causes according to the "80-20 rule"
• the length of a beach in Western Australia: Eighty Mile Beach
• the length of the Eighty Years' War or Dutch revolt (1568-1648)
• the number of the French department Somme
• the designation of Interstate 80, a freeway that runs from California to New York; the European route E80 from Lisbon to Gürbulak
• the standard TCP/IP port number for HTTP connection
• the 80A, 80B and 80C photographic filters correct for excessive redness under tungsten lighting
• The ISBN Group Identifier for books published in the Czech Republic and Slovakia.
• The year AD 80, 80 BC, or 1980.
• The Audi 80, the predecessor to the Audi A4.
• The title of the 8th track on Green Day's second full length album Kerplunk!
• The highest score possible on each of the three sections of the PSAT
• Eighty shilling ale
• A Dutch philosofical ideal.

[edit] External links

• wiktionary:eighty for 80 in other languages.

З