一个数如果恰好等于它的因子和，这个数就称为“完数”。例如，6的因子为1,2,3，而6=1+2+3，所以6是“完数”。 编程输出1000以内的所有完数，每个完数输出一行，并按下面的格式输出其因子： 6 its factors are 1,2,3

以下是Python代码实现：

for i in range(2, 1001):
    factors = []
    for j in range(1, i):
        if i % j == 0:
            factors.append(j)
    if sum(factors) == i:
        print(i, "its factors are", ",".join(str(x) for x in factors))

输出结果如下：

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