Primality proof for n = 288773:
Take b = 2.
b^(n-1) mod n = 1.
6563 is prime. b^((n-1)/6563)-1 mod n = 27424, which is a unit, inverse 233375.
(6563) divides n-1.
(6563)^2 > n.
n is prime by Pocklington's theorem.