Primality proof for n = 228572385721:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=272109983.html>272109983 is prime.</a>
<br>b^((n-1)/272109983)-1 mod n = 228249034434, which is a unit, inverse 195783320097.
<p>(272109983) divides n-1.
<p>(272109983)^2 > n.
<p>n is prime by Pocklington's theorem.