Primality proof for n = 23819:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=11909.html>11909 is prime.</a>
<br>b^((n-1)/11909)-1 mod n = 3, which is a unit, inverse 7940.
<p>(11909) divides n-1.
<p>(11909)^2 > n.
<p>n is prime by Pocklington's theorem.