Primality proof for n = 21347:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=821.html>821 is prime.</a>
<br>b^((n-1)/821)-1 mod n = 15242, which is a unit, inverse 10413.
<p>(821) divides n-1.
<p>(821)^2 > n.
<p>n is prime by Pocklington's theorem.