Primality proof for n = 7240687:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=1206781.html>1206781 is prime.</a>
<br>b^((n-1)/1206781)-1 mod n = 63, which is a unit, inverse 5746577.
<p>(1206781) divides n-1.
<p>(1206781)^2 > n.
<p>n is prime by Pocklington's theorem.