Primality proof for n = 21101:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=211.html>211 is prime.</a>
<br>b^((n-1)/211)-1 mod n = 4003, which is a unit, inverse 15408.
<p>(211) divides n-1.
<p>(211)^2 > n.
<p>n is prime by Pocklington's theorem.