Primality proof for n = 21258969373:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=121283.html>121283 is prime.</a>
<br>b^((n-1)/121283)-1 mod n = 4094585588, which is a unit, inverse 20258460660.
<p><a href=541.html>541 is prime.</a>
<br>b^((n-1)/541)-1 mod n = 898561711, which is a unit, inverse 2834262398.
<p>(541 * 121283) divides n-1.
<p>(541 * 121283)^2 > n.
<p>n is prime by Pocklington's theorem.