Is () an integer
The is an integer block is a boolean block and an operators block that detects if a number is an integer (is not a fraction or a decimal). To get this block, one must add the "Operators Expansion" extension.
Workaround
Taking (whatever) mod (1) reports 0 if the first input is a string or is an integer.
Rounding the number and seeing if it's the same as the original number also works.