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In number theory, a hemiperfect number is a positive integer with a half-integral abundancy index. For a given odd number ''k'', a number ''n'' is called ''k''-hemiperfect if and only if the sum of all positive divisors of ''n'' (the divisor function, ''σ''(''n'')) is equal to × n. == Smallest ''k''-hemiperfect numbers == The following table gives an overview of the smallest ''k''-hemiperfect numbers for ''k'' ≤ 17 : For example, 24 is 5-hemiperfect because the sum of the divisors of 60 is : 1 + 2 + 3 + 4 + 6 + 8 + 12 + 24 = 60 = × 24. 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「Hemiperfect number」の詳細全文を読む スポンサード リンク
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