Primality proof for n = 681148913:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=1123.html>1123 is prime.</a>
<br>b^((n-1)/1123)-1 mod n = 62040257, which is a unit, inverse 116464728.
<p><a href=227.html>227 is prime.</a>
<br>b^((n-1)/227)-1 mod n = 405588263, which is a unit, inverse 409503919.
<p>(227 * 1123) divides n-1.
<p>(227 * 1123)^2 > n.
<p>n is prime by Pocklington's theorem.