Primality proof for n = 509834927133261305493315894436753153401122015851834224693667:
Take b = 2.
b^(n-1) mod n = 1.
4019927965686165521481374447 is prime.
b^((n-1)/4019927965686165521481374447)-1 mod n = 20352885333208462250446576940059645482394302704267436806302, which is a unit, inverse 281815940571667965728091750299974632086037782025798268332680.
12779357438669681 is prime.
b^((n-1)/12779357438669681)-1 mod n = 77038841293553107386905600141879241787103449874553187372717, which is a unit, inverse 250604496401758659197204576455211016113735315895068148157001.
(12779357438669681 * 4019927965686165521481374447) divides n-1.
(12779357438669681 * 4019927965686165521481374447)^2 > n.
n is prime by Pocklington's theorem.