Primality proof for n = 1091:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=109.html>109 is prime.</a>
<br>b^((n-1)/109)-1 mod n = 1023, which is a unit, inverse 369.
<p>(109) divides n-1.
<p>(109)^2 > n.
<p>n is prime by Pocklington's theorem.