Primality proof for n = 18553:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=773.html>773 is prime.</a>
<br>b^((n-1)/773)-1 mod n = 5303, which is a unit, inverse 13606.
<p>(773) divides n-1.
<p>(773)^2 > n.
<p>n is prime by Pocklington's theorem.