It turns out that my adolescent son might have numeric synaesthesia-- numbers have specific colors and possibly other distinguishing characteristics for him. He has shown that he can commit long sequences of numbers to memory, apparently by breaking them into three-digit chunks and then just forming a visual memory of them.
First question: sure this helps him recall numbers, but it also means there is a bit of irrelevant information attached to each number he encounters, and that could be confusing or distracting while learning math (e.g. two numbers "clash" so the answer feels wrong even though it isn't). Does anybody have any advice for me or him on good practices, on problems to be alert for, etc.?
Second question (a fun one): can anybody think of practical/entertaining things he can do with the ability to recall long strings of numbers?