def checkio(number):
ret = []
for i in range(9, 1, -1):
while not number % i:
number /= i
ret.append(i)
if number == 1:
return int(''.join(map(str, sorted(ret))))
return 0
if __name__ == '__main__':
#These "asserts" using only for self-checking and not necessary for auto-testing
assert checkio(20) == 45, "1st example"
assert checkio(21) == 37, "2nd example"
assert checkio(17) == 0, "3rd example"
assert checkio(33) == 0, "4th example"
assert checkio(3125) == 55555, "5th example"
assert checkio(9973) == 0, "6th example"
http://www.checkio.org/mission/number-factory/