Primality proof for n = 855109789:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=5481473.html>5481473 is prime.</a>
<br>b^((n-1)/5481473)-1 mod n = 487410094, which is a unit, inverse 809122865.
<p>(5481473) divides n-1.
<p>(5481473)^2 > n.
<p>n is prime by Pocklington's theorem.