The factor is less than 2^64, so it shouldnøt be neccesary to use the largesieve submission page (but I have tried anyway).

It is version 24.6.

As it's rather easy to test I was hoping someone had a program they could test it in, or perhaps someone else might try to factor the number with another program, so we might know whether there is a factor that's just reported wrong.

I don't think we should trouble George until we know for sure that it's an error in mprime.