409 is an interesting prime number. If you remove any number of its digits, then you will get a number that is not prime.
Call a number with this property a minimal prime. Find all minimal primes.
(In reply to solution
640009 is not a minimal prime. If you remove the 6 and two 0's, then you will have 409, which is prime. Also, you missed 946669 in your list.
Posted by Math Man
on 2012-04-24 17:26:45