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48 (forty-eight) is the natural number following 47 and preceding 49. It is one third of a gross, or four dozens. == In mathematics == Forty-eight is the double factorial of 6, a highly composite number. Like all other multiples of 6, it is a semiperfect number. 48 is the second 17-gonal number. 48 is in abundance having an aliquot sum of 76. It is the lowest composite number to fall into the 41-aliquot tree having the 7 aliquot number sequence,(48, 76, 64, 63, 41, 1, 0). 48 is highly abundant with an aliquot sum 158% higher than itself. 48 is the smallest number with exactly ten divisors. There are 11 solutions to the equation φ(''x'') = 48, namely 65, 104, 105, 112, 130, 140, 144, 156, 168, 180 and 210. This is more than any integer below 48, making 48 a highly totient number. Since the greatest prime factor of 482 + 1 = 2305 is 461, which is clearly more than 48 twice, 48 is a Størmer number. 48 is in base 10 a Harshad number. It has 24, 2, 12, and 4 as factors. 48 is a Narcissistic number (but subtracted instead of added) as: |42 - 82| = 48 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「48 (number)」の詳細全文を読む スポンサード リンク
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