In order to check whether the number 9339 is a prime, you should check if it is divisible by any prime integer number 

equal to or less than   = 96.6 =~ 96 (rounded).


If no one of these prime numbers is a divisor to the given number (in your case to the number of 9339),

then the given number (i.e. the number of 9339, in your case) is a prime.