Primality proof for n = 20975237:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=2477.html>2477 is prime.</a>
<br>b^((n-1)/2477)-1 mod n = 3635240, which is a unit, inverse 4029905.
<p><a href=73.html>73 is prime.</a>
<br>b^((n-1)/73)-1 mod n = 6506576, which is a unit, inverse 1390842.
<p>(73 * 2477) divides n-1.
<p>(73 * 2477)^2 > n.
<p>n is prime by Pocklington's theorem.