Primality proof for n = 604703486621959:

Take b = 2.

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

216558437 is prime.
b^((n-1)/216558437)-1 mod n = 149757495094359, which is a unit, inverse 340097112345405.

(216558437) divides n-1.

(216558437)^2 > n.

n is prime by Pocklington's theorem.