Primality proof for n = 246608641:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=21407.html>21407 is prime.</a>
<br>b^((n-1)/21407)-1 mod n = 170583700, which is a unit, inverse 96349255.
<p>(21407) divides n-1.
<p>(21407)^2 > n.
<p>n is prime by Pocklington's theorem.