isinteger() for the int* and uint* classes
isfloat() for the single and double classes
class() to determine the exact class
isa() to test membership in a particular class
If you have a floating point number and you wish to know whether it is an integer, test whether mod(Number,1) is 0.
If you have a floating point number and you wish to know whether it is rational, then the answer is Yes it is (unless it is infinite or nan), as all floating point numbers are represented as rational fractions of powers of 2.
If your question has to do with the Symbolic Toolbox then the answers are different.
