Take b = 2.

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

1373 is prime.

b^((n-1)/1373)-1 mod n = 319855112, which is a unit, inverse 403552596.

71 is prime.

b^((n-1)/71)-1 mod n = 1508896854, which is a unit, inverse 67666692.

(71 * 1373) divides n-1.

(71 * 1373)^2 > n.

n is prime by Pocklington's theorem.