Primality proof for n = 63521:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=397.html>397 is prime.</a>
<br>b^((n-1)/397)-1 mod n = 23268, which is a unit, inverse 14892.
<p>(397) divides n-1.
<p>(397)^2 > n.
<p>n is prime by Pocklington's theorem.