Primality proof for n = 58309:

Take b = 2.

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

113 is prime.
b^((n-1)/113)-1 mod n = 2027, which is a unit, inverse 24480.

2 is prime.
b^((n-1)/2)-1 mod n = 58307, which is a unit, inverse 29154.

(2^2 * 113) divides n-1.

(2^2 * 113)^2 > n.

n is prime by Pocklington's theorem.