The final digit of all prime numbers is either: 1,2,3,5,7,9

Of those, 1 and 9 do not appear as single digit primes...

And 2 and 5 only appear as single digit primes.

Also, of the four digit primes, the final 3 digits can be any of those "final primes" listed above except 2 and 5, as long as the first digit is a 1 or a 2, with the exception of 1333.