problem 34
145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.
Find the sum of all numbers which are equal to the sum of the factorial of their digits.
Note: as 1! = 1 and 2! = 2 are not sums they are not included.
# 寻找各位数的阶乘等于自身的数,求所有的这样的数之和。
# 思路: 假设最大的数有n位,则10^n > n*9! > 10^(n-1), n最大为7
from math import factorial as fac i = 10 nummax = 2550000 while i < nummax: sum1 = 0 string = str(i) for j in string: sum1 += fac(int(j)) if sum1 == i: print(i) i += 1