除了1与本身以外,不能被其它正整数整除的自然数,叫做素数,又称为质数。例如2、3、5、7、11、13、17、19…,其中2是最小的素数,但是不存在最大的素数。早在公元前三百多年,古希腊数学家欧几里得就证明了素数有无穷多个,即不存在最大的素数。他的证明方法如下: 如果说只有有限个,那么,就可把它们从小到大统统写出来,记为P_1、P_2、…P_n,此外,再没有更大的素数了。然而 Except 1 and itself, a natural number that can not be divisible by other positive integers, called prime numbers, is also called prime numbers. For example 2, 3, 5, 7, 11, 13, 17, 19 ..., where 2 is the smallest prime but there is no largest prime. As early as 300 BC, the ancient Greek mathematician Euclid proves that there are infinitely many prime numbers, that is, there is no maximum prime number. His proof is as follows: If there are only a limited number of them, then write them all as small as large and write them as P_1, P_2, ... P_n. In addition, there is no more prime number. however