Using this calculator you can find if an input number is Fermat pseudoprime. The calculator uses Fermat primality test, based on Fermat's little theorem. If n is a prime number, and a is not divisible by n, then : .
But, the test does not say an input number is prime or not, even the result is 1. I.e. the converse is not true. if and a and n are coprime numbers does not mean n is a prime number.
E.g., the test on the number 29341 gives positive results using bases: 3; 5; 7; 11. However this number is not prime, it is the composite Carmichael number: 13 x 37 x 61= 29341.