Primality proof for n = 2520431:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=2083.html>2083 is prime.</a>
<br>b^((n-1)/2083)-1 mod n = 403849, which is a unit, inverse 1407694.
<p>(2083) divides n-1.
<p>(2083)^2 > n.
<p>n is prime by Pocklington's theorem.