# Method Gmp.mpz()->probably_prime_p()

Method probably_prime_p

  ``int(0..2)` probably_prime_p(`void`|`int` `count`)`

Description

  Return 2 if this mpz object is a prime, 1 if it probably is a prime, and 0 if it definitely is not a prime. Testing values below 1000000 will only return 2 or 0.

Parameter `count`

  The prime number testing is using Donald Knuth's probabilistic primality test. The chance for a false positive is pow(0.25,count). Default value is 25 and resonable values are between 15 and 50.