Challenge for you...

[bplus]

bplus
from the looks of it the code does one digit at a time judging from the \ 10 and mod 10, it would be many times faster if you did more digits at a time

And I do many digits at a time except maybe division in String Math but... all that String processing pays a price.
Update: Wait I do division by multiplying with reciprocals, that's right.

I was wondering if maybe do _Integer64 for maximizing number of integers maybe 12+ digits at a time?
6 of 1, half dozen of another...?