Primality proof for n = 1637:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=409.html>409 is prime.</a>
<br>b^((n-1)/409)-1 mod n = 15, which is a unit, inverse 764.
<p>(409) divides n-1.
<p>(409)^2 > n.
<p>n is prime by Pocklington's theorem.