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180 (one hundred () eighty) is the natural number following 179 and preceding 181. ==In mathematics== 180 is an abundant number, with its proper divisors summing up to 366.〔(【引用サイトリンク】url=http://www.virtuescience.com/180.html ) 〕 180 is also a highly composite number, a positive integer with more divisors than any smaller positive integer. One of the consequences of 180 having so many divisors is that it is a practical number, meaning that any positive number smaller than 180 that is not a divisor of 180 can be expressed as the sum of some of 180's divisors. 180 is the sum of two square numbers: 122 + 62. It can be expressed as either the sum of six consecutive prime numbers: 19 + 23 + 29 + 31 + 37 + 41, or the sum of eight consecutive prime numbers: 11 + 13 + 17 + 19 + 23 + 29 + 31 + 37. 180 is an Ulam number, which can be expressed as a sum of earlier terms in the Ulam sequence only as 177 + 3. 180 is a 61-gonal number.〔 Half a circle has 180 degrees. Summing Euler's totient function φ(''x'') over the first + 24 integers gives 180. 180 is a Harshad number in base 10, and in binary it is a digitally balanced number, since its binary representation has the same number of zeros as ones (10110100). 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「180 (number)」の詳細全文を読む スポンサード リンク
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