Primality proof for n = 409477:
Take b = 2.
b^(n-1) mod n = 1.
34123 is prime. b^((n-1)/34123)-1 mod n = 4095, which is a unit, inverse 391678.
(34123) divides n-1.
(34123)^2 > n.
n is prime by Pocklington's theorem.