!!SuperPrime

!!SuperPrime is a language created by anonymous Esolangs user 100.1.142.136 in which the empty program is a prime checker.

The only command is a line of no characters.

An implementation in Pyth

>2lPQ

Or, an alternate implementation in J:

SP =: (0 0$0)"_`(1&p:@[)@.(''-:])

Call like:

input SP program

Example:

   2 SP 
1
   2 SP '4'
   3 SP '4'
   4 SP '4'
   4 SP 
0