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.