80 (eighty) is the natural number following 79 and preceding 81. ← 79 81 → 80 ← 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 eighty Ordinal 80th (eightieth) Numeral system 80 Factorization Divisors 1, 2, 4, 5, 8, 10, 16, 20, 40, 80 Roman numeral LXXX Binary 10100002 Octal 1208 Duodecimal 6812 Hexadecimal 5016 Contents 1 In mathematics 2 In science 3 In religion 4 In sports 5 In other fields 6 References 7 External links 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 ménage number, and is a Harshad number number in base 10. The Pareto principle (also known as the "80-20 rule," states that, for many events, roughly 80% of the effects come from 20% of the causes.12 In science Element 80: Mercury (Hg) The atomic number of mercury A rectifier vacuum tube manufactured from the mid-1920s through the mid-1980s, the longest production run of any American vacuum tube.citation needed In religion

According to Exodus 7:7, Moses was 80 years old when he initially spoke to Pharaoh on behalf of his people. Today, 80 years of age is the upper age limit for cardinals to vote in papal elections. In sports Jerry Rice wore the number 80 for the majority of his NFL career. The number 80 is also the retired number of Seattle Seahawks wide receiver Steve Largent; when Rice was traded to the Seahawks, Largent gave the team permission to unretire his number so Rice could wear it. In other fields

Eighty is also: the length of the Eighty Years' War or Dutch revolt (1568–1648) the standard TCP/IP port number for HTTP connections the 80A, 80B and 80C photographic filters correct for excessive redness under tungsten lighting The year AD 80, 80 BC, or 1980. The highest score possible on each of the three sections of the PSAT Eighty shilling ale I-80 is an interstate highway going from New York to San Francisco The older four-pin-base version of the 5Y3GT rectifier tube A common limit for the characters per line, in computing, derived from the number of columns in IBM cards References ^ Bunkley, Nick (March 3, 2008), "Joseph Juran, 103, Pioneer in Quality Control, Dies", New York Times, http://www.nytimes.com/2008/03/03/business/03juran.html . ^ What is 80/20 Rule, Pareto’s Law, Pareto Principle, http://www.80-20presentationrule.com/whatisrule.html . External links Wikimedia Commons has media related to: 80 (number) wiktionary:eighty for 80 in other languages.