Is it possible to check if a string has any numbers in it?

I'm making chat commands, and I want to be able to find any sort of number in a command. I know you can use string.find to find a specific number, but I'm trying to find any number. I also know you can use string.sub, but that won't work well with a command that can vary in length. Does anyone know a for sure way to get a number in a string value, and only the number?