Primality proof for n = 28287053:

Take b = 2.

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

7071763 is prime.
b^((n-1)/7071763)-1 mod n = 15, which is a unit, inverse 24515446.

(7071763) divides n-1.

(7071763)^2 > n.

n is prime by Pocklington's theorem.