> Any number, if you define them as a representation of digits, is computable in that sense. You have to be a bit careful, here. What you're saying is true of

> Any number, if you define them as a representation of digits, is computable in that sense. You have to be a bit careful, here. What you're saying is true of integers (such as the values taken by the BB function), as well as rationals. But it's not true of real numbers, because the reals are uncountable, and therefore there are infinitely many real numbers that cannot be finitely "described" or written down (in whatever notation you happen to care about). An example of an uncomputable real number: https://en.wikipedia.org/wiki/Chaitin%27s_constant https://en.wikipedia.org/wiki/Chaitin%27s_constant