If a number is a natural number it is a complex number

The answer to this is yes. Natural numbers are a subset of the integers which are a subset of the reals which are complex numbers. A complex number can also be written as a+bi, which a real number has imaginary part 0, so just a. An integer is a number that can be written without a fractional or decimal component, and a natural number is an integer that is at least 0. Either way, a natural number is a complex number.