Primality proof for n = 603103:

Take b = 2.

b^(n-1) mod n = 1.

100517 is prime.
b^((n-1)/100517)-1 mod n = 63, which is a unit, inverse 449934.

(100517) divides n-1.

(100517)^2 > n.

n is prime by Pocklington's theorem.