Primality proof for n = 79806171026243:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=21258969373.html>21258969373 is prime.</a>
<br>b^((n-1)/21258969373)-1 mod n = 3794218842250, which is a unit, inverse 51000527180810.
<p>(21258969373) divides n-1.
<p>(21258969373)^2 > n.
<p>n is prime by Pocklington's theorem.