First, in order to get to know if 256 it is a rational or irrational number we have to begin with the definition of what is rational and irrational number.
Rational numbers are all the number that can be represented as fractions, while the irrational numbers are all the numbers that can not be expressed as fractions.
In this case, then we can confirm that the number 256 can be considered as a rational number because it can be expressed as the quotient of the two integers: for example 256/1.