snowball prime

A snowball prime also known as a right-truncatable prime, is a prime number whose digits can be chopped off, one by one, from the right-hand side, yet still leave a prime number. This means that even if you stop writing before you finish the number, you will still have written a prime. The largest snowball prime is 73939133 (7, 73, 739, ..., 73939133 are all prime).