一个数如果恰好等于它的因子之和，这个数就称为完数，C语言编程序找出1000之内的所有完数并按照6 its factors are 1，2，3的格式输出

以下是C语言编写的程序，实现了找出1000之内的所有完数并按照6 its factors are 1，2，3的格式输出的功能：

#include <stdio.h>

int main() {
    int i, j, sum;
    printf("The perfect numbers between 1 and 1000 are:\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 1", i);
            for (j = 2; j <= i/2; j++) {
                if (i % j == 0) {
                    printf(", %d", j);
                }
            }
            printf("\n");
        }
    }
    return 0;
}

程序运行结果如下：

The perfect numbers between 1 and 1000 are:
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