I don't see many 50 digits factors with B1=1e6 ...

Code:

Run 178 out of 200:
Using B1=1000000, B2=1045563762, polynomial Dickson(6), sigma=2726828695
Step 1 took 2276ms
Step 2 took 1436ms
********** Factor found in step 2: 20819759916248446572812979296981961157835787899653
Found probable prime factor of 50 digits: 20819759916248446572812979296981961157835787899653
Probable prime cofactor 2944668849437874913553507825327499221600601795476762700186109016306167187 has 73 digits