Primality proof for n = 28181:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=1409.html>1409 is prime.</a>
<br>b^((n-1)/1409)-1 mod n = 5878, which is a unit, inverse 16200.
<p>(1409) divides n-1.
<p>(1409)^2 > n.
<p>n is prime by Pocklington's theorem.