Primality proof for n = 19699:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=67.html>67 is prime.</a>
<br>b^((n-1)/67)-1 mod n = 15223, which is a unit, inverse 17987.
<p><a href=7.html>7 is prime.</a>
<br>b^((n-1)/7)-1 mod n = 1503, which is a unit, inverse 15636.
<p>(7^2 * 67) divides n-1.
<p>(7^2 * 67)^2 > n.
<p>n is prime by Pocklington's theorem.