80 (number) - Wikipedia2022-08-24
In mathematics. 80 is: . the sum of Euler's totient function φ(x) over the first sixteen integers.; a semiperfect number, since adding up some subsets of its divisors (e.g., 1, 4, 5, 10, 20 and 40) gives 80.; a ménage number.; palindromic in bases 3 (2222 3), 6 (212 6), 9 (88 9), 15 (55 15), 19 (44 19) and 39 (22 39).; a repdigit in bases 3, 9, 15, 19 and 39.; The Pareto
了解详情