80 (number)
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Appearance
From Wikipedia, the free encyclopedia
(Redirected from Number 80)
Natural number
| Cardinal | eighty |
|---|---|
| Ordinal | 80th (eightieth) |
| Numeral system | octogesimal |
| Factorization | 24 ×ばつ 5 |
| Divisors | 1, 2, 4, 5, 8, 10, 16, 20, 40, 80 (10) |
| Greek numeral | Π ́ |
| Roman numeral | LXXX, lxxx |
| Binary | 10100002 |
| Ternary | 22223 |
| Senary | 2126 |
| Octal | 1208 |
| Duodecimal | 6812 |
| Hexadecimal | 5016 |
| Armenian | Ձ |
| Hebrew | פ / ף |
| Babylonian numeral | 𒐕⟪ |
| Egyptian hieroglyph | 𓎍 |
80 (eighty) is the natural number following 79 and preceding 81.
In mathematics
[edit ]80 is:
- The sum of Euler's totient function φ(x) over the first sixteen integers:
- 1 +たす 1 +たす 2 +たす 2 +たす 4 +たす 2 +たす 6 +たす 4 +たす 6 +たす 4 +たす 10 +たす 4 +たす 12 +たす 6 +たす 8 +たす 8 =わ 80.
- A semiperfect number, since adding up some subsets of its divisors (e.g., 1, 4, 5, 10, 20, and 40) gives 80.[1]
- A ménage number.[2]
- Palindromic in bases 3 (22223), 6 (2126), 9 (889), 15 (5515), 19 (4419), and 39 (2239).
- A repdigit in bases 3, 9, 15, 19, and 39.
- The sum of the first four twin prime pairs:
- (3 + 5) + (5 + 7) + (11 + 13) + (17 + 19) = 80.
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.[3] [4]
Every solvable configuration of the 15 puzzle can be solved in no more than 80 single-tile moves.[5]
In trade
[edit ]In Northern Europe, there have traditionally been words for eighty units - often eggs or herrings: Wall [de; da; no] in German, ol in Danish, and øll in Norwegian (all cognates).
References
[edit ]- ^ "Sloane's A005835: Pseudoperfect (or semiperfect) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016年05月29日.
- ^ "Sloane's A000179: Ménage numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016年05月29日.
- ^ Bunkley, Nick (March 3, 2008). "Joseph Juran, 103, Pioneer in Quality Control, Dies". The New York Times .
- ^ "What is 80/20 Rule, Pareto's Law, Pareto Principle". Archived from the original on 2013年01月28日. Retrieved 2017年05月20日.
- ^ A. Brüngger, A. Marzetta, K. Fukuda, and J. Nievergelt, The parallel search bench ZRAM and its applications, Annals of Operations Research 90 (1999), pp. 45–63.
External links
[edit ]Wikimedia Commons has media related to 80 (number) .
- wiktionary:eighty for 80 in other languages.