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60 (sixty) () is the natural number following 59 and preceding 61. Being three times 20, it is called "three score" in older literature. ==In mathematics== It is a composite number, with divisors 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, and 60, making it a highly composite number. Because it is the sum of its unitary divisors (excluding itself), it is a unitary perfect number, and it is an abundant number with an abundance of 48. Being ten times a perfect number, it is a semiperfect number. It is the smallest number divisible by the numbers 1 to 6: there is no smaller number divisible by the numbers 1 to 5. It is the smallest number with exactly 12 divisors. It is one of seven integers that have more divisors than a number twice itself , one of six that are also lowest common multiple of a consecutive set of integers from 1, and one of six that are divisors of every highly composite number higher than itself. It is the sum of a pair of twin primes (29 + 31) and the sum of four consecutive primes (11 + 13 + 17 + 19). It is adjacent to two primes (59 and 61). It is the smallest number that is the sum of two odd primes in six ways.〔Wells, D. ''The Penguin Dictionary of Curious and Interesting Numbers'' London: Penguin Group. (1987): 109–110.〕 The smallest non-solvable group (A5) has order 60. There are four Archimedean solids with 60 vertices: the truncated icosahedron, the rhombicosidodecahedron, the snub dodecahedron, and the truncated dodecahedron. The skeletons of these polyhedra form 60-node vertex-transitive graphs. There are also two Archimedean solids with 60 edges: the snub cube and the icosidodecahedron. The skeleton of the icosidodecahedron forms a 60-edge symmetric graph. There are 60 one-sided hexominoes, the polyominoes made from six squares. In geometry, it is the number of seconds in a minute, and the number of minutes in a degree. In normal space, the three interior angles of an equilateral triangle each measure 60 degrees, adding up to 180 degrees. Because it is divisible by the sum of its digits in base 10, it is a Harshad number. A number system with base 60 is called sexagesimal (the original meaning of ''sexagesimal'' is sixtieth). It is the smallest positive integer that is written with only the smallest and the largest digit of base 2 (binary), base 3 (ternary) and base 4 (quaternary). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「60 (number)」の詳細全文を読む スポンサード リンク
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