Primality proof for n = 63863:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=863.html>863 is prime.</a>
<br>b^((n-1)/863)-1 mod n = 16462, which is a unit, inverse 28859.
<p>(863) divides n-1.
<p>(863)^2 > n.
<p>n is prime by Pocklington's theorem.