Primality proof for n = 407723:

Take b = 2.

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

29123 is prime.
b^((n-1)/29123)-1 mod n = 16383, which is a unit, inverse 2862.

(29123) divides n-1.

(29123)^2 > n.

n is prime by Pocklington's theorem.