Primality proof for n = 15137:
Take b = 2.
b^(n-1) mod n = 1.
43 is prime.
b^((n-1)/43)-1 mod n = 9610, which is a unit, inverse 14833.
11 is prime.
b^((n-1)/11)-1 mod n = 11802, which is a unit, inverse 4734.
(11 * 43) divides n-1.
(11 * 43)^2 > n.
n is prime by Pocklington's theorem.