Now I got my second factor on mersenne.ca. This one is a factor of M9999971879: 17120076576497274889 divides M9999971879 TF 63-64...

I got this new Mersenne factor of 22 digits while doing trial-factoring of M773,833,681.

This will be quite a long post. M11=23*89 factored year 1536 M23=47*178481 factored year 1640 M41=13367*164511353 factored year 1859...