Primality proof for n = 3623:
Take b = 2.
b^(n-1) mod n = 1.
1811 is prime. b^((n-1)/1811)-1 mod n = 3, which is a unit, inverse 1208.
(1811) divides n-1.
(1811)^2 > n.
n is prime by Pocklington's theorem.