Maple says it is, Rabin-Miller says it is, the 2/3 of APR-CL I've done say it isnt. Most likely explanation is a bug in my code, but my code gives correct answer for many of the prime test vectors.....so I'd like a definitive answer, if anyone can see a way to find one. The number is: 239801962168368680208308065866293972540927 Cheers, Alan