I was quite gifted at math, first place out of a school year of 250+ students. I know as an adult that I have all nm for all 0<n,m<10 memorised. When I see something like 79 I use memory and not logic.

I feel a lot of math is made easier once some facts become so simple they're memorised. I can do large arithmetic quite easily in my head due to having the basics memorised.