Primality proof for n = 10019573:

Take b = 2.

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

80803 is prime.
b^((n-1)/80803)-1 mod n = 2007763, which is a unit, inverse 1014871.

(80803) divides n-1.

(80803)^2 > n.

n is prime by Pocklington's theorem.