Primality proof for n = 27563049583:

Take b = 2.

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

3028241 is prime.
b^((n-1)/3028241)-1 mod n = 12238328464, which is a unit, inverse 26245178574.

(3028241) divides n-1.

(3028241)^2 > n.

n is prime by Pocklington's theorem.