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.