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130 (number) : ウィキペディア英語版 | 130 (number)
130 (one hundred () thirty) is the natural number following 129 and preceding 131. ==In mathematics== 130 is a sphenic number. It is a noncototient since there is no answer to the equation ''x'' - φ(''x'') = 130. 130 is the only integer that is the sum of the squares of its first four divisors, including 1: 12 + 22 + 52 + 102 = 130. 130 is the largest number that cannot be written as the sum of four hexagonal numbers.〔(MathWorld - Hexagonal Number )〕
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