Primality proof for n = 13331831:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=1373.html>1373 is prime.</a>
<br>b^((n-1)/1373)-1 mod n = 1207233, which is a unit, inverse 1512291.
<p><a href=971.html>971 is prime.</a>
<br>b^((n-1)/971)-1 mod n = 2792113, which is a unit, inverse 10572798.
<p>(971 * 1373) divides n-1.
<p>(971 * 1373)^2 > n.
<p>n is prime by Pocklington's theorem.