Primality proof for n = 337973:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=4447.html>4447 is prime.</a>
<br>b^((n-1)/4447)-1 mod n = 88713, which is a unit, inverse 135017.
<p>(4447) divides n-1.
<p>(4447)^2 > n.
<p>n is prime by Pocklington's theorem.