用C语言一个数如果恰好等于它的因子之和，这个数就称为“完数”。例如，6的因子为1，2，3，且6=1+2+3，因此6是“完数”。编程找出1000之内的所有完数，按如下格式输出其因子：6 its factors are 1 2 3

以下是C语言代码实现：

#include <stdio.h>

int main() {
    int i, j, sum;

    printf("Perfect numbers within 1000: \n");

    for (i = 1; i <= 1000; i++) {
        sum = 0;
        for (j = 1; j < i; j++) {
            if (i % j == 0) {
                sum += j;
            }
        }
        if (sum == i) {
            printf("%d its factors are ", i);
            for (j = 1; j < i; j++) {
                if (i % j == 0) {
                    printf("%d ", j);
                }
            }
            printf("\n");
        }
    }

    return 0;
}

运行结果如下：

Perfect numbers within 1000: 
6 its factors are 1 2 3 
28 its factors are 1 2 4 7 14 
496 its factors are 1 2 4 8 16 31 62 124 248