Primality proof for n = 66721073718023:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=91309423.html>91309423 is prime.</a>
<br>b^((n-1)/91309423)-1 mod n = 63631457236067, which is a unit, inverse 58727005515932.
<p>(91309423) divides n-1.
<p>(91309423)^2 > n.
<p>n is prime by Pocklington's theorem.