Normally MEL figures out whether a number is an integer or a float based on whether it has a decimal part. You can force a number to be an integer or float by declaring its type explicitly:
(float) 7
// The number is floating point.
(int) 7.5
// The number is integer (MEL automatically truncates to 7)
You can also explicitly state that a value is a string, even if it doesn’t exactly look like one:
(string) 500
// This is the same as "500"
(string) 56.56
// This is the same as "56.56"
Maya automatically converts numbers to strings or vice versa when you use them together and it’s obvious what you meant.
Be careful: some cases are ambiguous, and what MEL chooses to do may not be what you meant. For example:
print("500" + 5);
Prints: 5005 (the string "500” with the string “5” added on the end), not 505 (the number 500 plus 5).