Take b = 2.

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

2843 is prime.

b^((n-1)/2843)-1 mod n = 2032800, which is a unit, inverse 1672325.

43 is prime.

b^((n-1)/43)-1 mod n = 1227293, which is a unit, inverse 3088149.

(43 * 2843) divides n-1.

(43 * 2843)^2 > n.

n is prime by Pocklington's theorem.