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是完数，因为6=1+2+3。编程求1000之内的所有完数，并按下面格式输出其因子：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 == :
            factors.append(j)
    if sum(factors) == i:
        print(i, "its factors are", ",".join(str(x) for x in factors))

输出结果为：

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