def solution():
s = "123456789"
max_pan_digit = 0
for i in range(9,4,-1):
for num in permute(s[:i]):
num = int(num)
if num > max_pan_digit and is_prime(num):
max_pan_digit = num
print "done with:",i,"max so far:",max_pan_digit
return max_pan_digit
def check_primes(num_list):
for item in num_list:
if not is_prime(item):
return False
return True
