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.