[charcircuit]

Big O notation is often used with assumptions like adding numbers is always constant time. You can't physically build a machine where addition between any two numbers is constant time, but that doesn't matter.

[xvedejas]

It depends what you mean by "numbers": all integers or just 64-bit ones?

[charcircuit]

My point is relevant to additions that are the same type as n as n has no upper bound. n will never be a 64 bit integer.