For example a number whose domain would be all positive would be described as a number k, where k > 0. How would you describe a number that is an integer, ie not 1.4, 7.666 et cetera. I can't think of a way to define this mathematically (or a way that includes any number of digits). I know there is a way though, considering the data type "int" that would be used i a computer programming language. thanks for any input!