Primality proof for n = 28687:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=683.html>683 is prime.</a>
<br>b^((n-1)/683)-1 mod n = 26969, which is a unit, inverse 13542.
<p>(683) divides n-1.
<p>(683)^2 > n.
<p>n is prime by Pocklington's theorem.