Primality proof for n = 250681:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=2089.html>2089 is prime.</a>
<br>b^((n-1)/2089)-1 mod n = 157963, which is a unit, inverse 148549.
<p>(2089) divides n-1.
<p>(2089)^2 > n.
<p>n is prime by Pocklington's theorem.