Take b = 2.

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

211 is prime.

b^((n-1)/211)-1 mod n = 3834, which is a unit, inverse 115218.

19 is prime.

b^((n-1)/19)-1 mod n = 100400, which is a unit, inverse 3262.

(19 * 211) divides n-1.

(19 * 211)^2 > n.

n is prime by Pocklington's theorem.