Primality proof for n = 863:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=431.html>431 is prime.</a>
<br>b^((n-1)/431)-1 mod n = 3, which is a unit, inverse 288.
<p>(431) divides n-1.
<p>(431)^2 > n.
<p>n is prime by Pocklington's theorem.