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101 (one hundred () one) is the natural number following 100 and preceding 102. It is variously pronounced "one hundred and one" / "a hundred and one", "one hundred one" / "a hundred one", and "one oh one". As an ordinal number, 101st (one hundred () first) rather than 101th is the correct form. ==In mathematics== 101 is the 26th prime number and a palindromic number (and so a palindromic prime). The next prime is 103, with which it makes a twin prime pair, making 101 a Chen prime. Because the period length of its reciprocal is unique among primes, 101 is a unique prime. 101 is an Eisenstein prime with no imaginary part and real part of the form . 101 is the sum of five consecutive primes (13 + 17 + 19 + 23 + 29). Given 101, the Mertens function returns 0. 101 is the fifth alternating factorial. 101 is a centered decagonal number. The decimal representation of 2^101-1 is 2 535301 200456 458802 993406 410751. The prime decomposition of that is 7 432339 208719 x 341117 531003 194129 For a 3-digit number in base 10, this number has a relatively simple divisibility test. The candidate number is split into groups of four, starting with the rightmost four, and added up to produce a 4-digit number. If this 4-digit number is of the form 1000''a'' + 100''b'' + 10''a'' + ''b'' (where ''a'' and ''b'' are integers from 0 to 9), such as 3232 or 9797, or of the form 100''b'' + ''b'', such as 707 and 808, then the number is divisible by 101. On the seven-segment display of a calculator, 101 is both a strobogrammatic prime and a dihedral prime. 101 is the only existing prime with alternating 1s and 0s in base 10 and the largest known prime of the form 10''n'' + 1.〔Prime Curios! (101 )〕 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「101 (number)」の詳細全文を読む スポンサード リンク
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