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127 (one hundred () twenty-seven) is the natural number following 126 and preceding 128. It is also a prime number. == In mathematics == *As a Mersenne prime, 127 is related to the perfect number 8128. 127 is also an exponent for another Mersenne prime 2127 - 1 (2127 - 1), which was discovered by Édouard Lucas in 1876, and held the record for the largest known prime for 75 years - it is still the largest prime ever discovered by hand calculations. Furthermore, 127 is equal to 27 - 1, and because 7 is also a Mersenne prime, this makes 127 a double Mersenne prime. *127 is also a cuban prime of the form , . The next prime is 131, with which it comprises a cousin prime. Because the next odd number, 129, is a semiprime, 127 is a Chen prime. 127 is greater than the arithmetic mean of its two neighboring primes, thus it is a strong prime. *127 cannot be written as a sum of a power of 2 and a prime, the next is 149. *127 is a centered hexagonal number. *It is the 7th Motzkin number. *127 is a palindromic prime in nonary and binary. *It is the first nice Friedman number in base 10, since 127 = -1 + 27, as well as binary since 1111111 = (1 + 1)111 - 1 * 1. 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「127 (number)」の詳細全文を読む スポンサード リンク
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