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1000 or one thousand is the natural number following 999 and preceding 1001 in most English-speaking countries. It is conventionally written with a comma separating the thousands unit: 1,000. It may also be described as the short thousand in historical discussion of medieval contexts where it might be confused with the Germanic concept of the "long thousand" (1200). == In mathematics == *The decimal representation for one thousand is * *1,000—a one followed by three zeros, in the general notation ; * *1 × 103—in engineering notation, which for this number coincides with : * *1 × 103 exactly—in scientific normalized exponential notation ; * *1 E+3 exactly—in scientific E notation. *The SI prefix for a thousand is kilo-, officially abbreviated as k—for instance, prefixed to "metre" or its abbreviation ''m'', ''kilometre'' or ''km'' signifies a thousand metres. As such, people occasionally represent the number in a non-standard notation by replacing the last three zeros of the general numeral with "K": for instance, 30K for 30,000. *By the SI writing style, a space can be used to as a thousands separator, i.e., to separate the digits of a number every power of 1000. *The sum of Euler's totient function over the first 57 integers is 1000. * (Prime Curios! ) mentions that 1000 is the smallest number that generates three primes in the fastest way possible by concatenation of decremented numbers (1000999, 1000999998997, and 1000999998997996995994993 are prime). The criterion excludes counting the number itself. * 1000 is a Harshad number in base 10. 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「1000 (number)」の詳細全文を読む スポンサード リンク
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