Take b = 2.

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

490812343031 is prime.
b^((n-1)/490812343031)-1 mod n = 168666067834047, which is a unit, inverse 72442089171299.

(490812343031) divides n-1.

(490812343031)^2 > n.

n is prime by Pocklington's theorem.