He's gonna be great at base-25 math.
He's well equipped for the digital age. Of course, if he enters a life of crime, he may avoid the long arm of the law, who will need to be on their toes figuring out how to properly employ a ten-print card on him.
Well, the Schoolhouse Rock for the 12 multiplication tables is about an alien with 12 toes and goes into base-12 match (1-9, dec, el, and do). I didn't really get it until years after seeing it. In any event, that could be useful with his 12 fingers, even though he has 13 toes. I always thought that it was too bad that we didn't have 4 fingers on each hand and 4 toes on each foot like a cartoon character. If we had, we'd all naturally be doing octal or hexidecimal mathematics, which would make computing a whole lot easier.