分解质因数： 每个非素数（合数）都可以写成几个素数（也可称为质数）相乘的形式，这几个素数就都叫做这个合数的质因数

#include<stdio.h>int prine(int i);int main(){int number, c, d;scanf("%d", &number);c =  prine(number);printf("%d=", number);if (!c){printf("%d", number);}else{int i = 2;do {if (!prine(i)){while (number%i == 0){if (number%i == 0 && number / i != 1) printf("%dx", i);else if (number%i == 0 && number / i == 1) printf("%d", i);number /= i;} }i++;} while (number != 1);}system("pause");return 0;}int prine(int i){int c=0, d;for (int b = 2; b < i; b++){d = i%b;if (!d){c = 1;break;}}return c;}