Primality proof for n = 3981375605939564164049:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=998970029.html>998970029 is prime.</a>
<br>b^((n-1)/998970029)-1 mod n = 747785645836125837029, which is a unit, inverse 3347458337248753549721.
<p><a href=3678217.html>3678217 is prime.</a>
<br>b^((n-1)/3678217)-1 mod n = 3184443142246297328418, which is a unit, inverse 1150790250003688746288.
<p>(3678217 * 998970029) divides n-1.
<p>(3678217 * 998970029)^2 > n.
<p>n is prime by Pocklington's theorem.