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。求1000之内的所有完数

以下是C语言代码，用于找出1000之内的所有完数，并按照指定格式输出其因子：

#include <stdio.h>

int main() {
    int i, j, sum;
    printf("完数有：\n");
    for (i = 2; i < 1000; i++) {
        sum = 0;
        for (j = 1; j < i; j++) {
            if ((i % j) == 0) {
                sum = j + sum;
            }
        }
        if (i == sum) {
            printf("%d its factors are ", i);
            for (j = 1; j < i; j++) {
                if ((i % j) == 0) {
                    printf("%d,", j);
                }
            }
            printf("\b.\n");
        }
    }
    return 0;
}

输出结果为：

完数有：
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.