Primality proof for n = 155317:

Take b = 2.

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

43 is prime.
b^((n-1)/43)-1 mod n = 23631, which is a unit, inverse 148074.

(43^2) divides n-1.

(43^2)^2 > n.

n is prime by Pocklington's theorem.