[mumblemumble]

The intent of that sentence is a lot clearer if you also consider the subsequent text, which expands on the idea quite a bit:

> Computers can only natively store integers, so they need some way of representing decimal numbers. This representation comes with some degree of inaccuracy. . . Why does this happen? It's actually pretty simple. When you have a base 10 system (like ours), it can only express fractions that use a prime factor of the base. . .

Perhaps a more formally correct way to put it is that integers (and natural numbers) are the only numbers that a computer can manage in a way that behaves reasonably similarly to the corresponding mathematic set. Specifically, as long as you stick to their numeric range, computer ints behave like a group, just like real integers do. But IEEE floats break the definition of a field in every which way, so they're really not a great match for the rationals.

That said, you could represent the rationals as a pair of integers, and that would be better-behaved, and some programming languages do do that. But I'm not aware of an ISA that supports it directly.