They're counting in logarithmic values and condensing millions of sequences of numbers in under a minute while the teacher is just calling him clever, yet they still use a horse and carriage as a method of travel and need to hire a kid to manually sort physical books (while threatening to kill him if the information gets leaked).
Also to the people talking about how Yiruki is acting, "savant syndrome" or "idiot savant" (Whatever you want to call it), comes with a lot of social impairment which is why he acts the way he does (it's like/is autism).