Whatever put it together in the first place had like 72 fingers.
It's all been downhill since the abacus. Slide rules are Okay for significant digits, but abaci are digital.
Quote:
Neurological analysis
Learning how to calculate with the abacus may improve capacity for mental calculation. Abacus-based mental calculation (AMC), which was derived from the abacus, is the act of performing calculations, including addition, subtraction, multiplication, and division, in the mind by manipulating an imagined abacus. It is a high-level cognitive skill that runs calculations with an effective algorithm. People doing long-term AMC training show higher numerical memory capacity and experience more effectively connected neural pathways.[52][53] They are able to retrieve memory to deal with complex processes
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en.wikipedia.org/wiki/Abacus#Neurological_analysis
You won't connect your motor memory to the result with a pocket calculator, it's too obscured.