Primality proof for n = 200639:

Take b = 2.

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

2333 is prime.
b^((n-1)/2333)-1 mod n = 193366, which is a unit, inverse 102623.

(2333) divides n-1.

(2333)^2 > n.

n is prime by Pocklington's theorem.