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71 (seventy-one) is the natural number following 70 and preceding 72. ==In mathematics== 71 is the algebraic degree of Conway's constant, a remarkable number arising in the study of look-and-say sequences. It is the 20th prime number. The next is 73, with which it composes a twin prime. It is also a permutable prime with 17. If we add up the primes less than 71 (2 through 67), we get 568, which is divisible by 71, 8 times. 71 is the largest (15th) supersingular prime, which is also a Chen prime. Also, 712 = 7! + 1, making it part of the last known pair of Brown numbers, as (71, 7). It is an Eisenstein prime with no imaginary part and real part of the form 3''n'' – 1. Since 9! + 1 is divisible by 71 but 71 is not one more than a multiple of 9, 71 is a Pillai prime. As 71 is the least prime factor of one more than the product of the first twenty-two terms of the Euclid–Mullin sequence, it is the twenty-third term. Also, 71 is the largest number which occurs as a prime factor of an order of a sporadic simple group. 71 is a centered heptagonal number. 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「71 (number)」の詳細全文を読む スポンサード リンク
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