Primality proof for n = 19851313:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=1097.html>1097 is prime.</a>
<br>b^((n-1)/1097)-1 mod n = 3689605, which is a unit, inverse 3614956.
<p><a href=13.html>13 is prime.</a>
<br>b^((n-1)/13)-1 mod n = 4216008, which is a unit, inverse 8865831.
<p>(13 * 1097) divides n-1.
<p>(13 * 1097)^2 > n.
<p>n is prime by Pocklington's theorem.