Primality proof for n = 1640653301747:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=820326650873.html>820326650873 is prime.</a>
<br>b^((n-1)/820326650873)-1 mod n = 3, which is a unit, inverse 546884433916.
<p>(820326650873) divides n-1.
<p>(820326650873)^2 > n.
<p>n is prime by Pocklington's theorem.