Primality proof for n = 21107:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=173.html>173 is prime.</a>
<br>b^((n-1)/173)-1 mod n = 13605, which is a unit, inverse 13322.
<p>(173) divides n-1.
<p>(173)^2 > n.
<p>n is prime by Pocklington's theorem.