You can access it the same way, it’s a different parsing issue here, to do it, use a slightly different syntax:
(1).toString()
Numbers can have decimals, so the syntax for ending in a decimal is a bit ambiguous when you go to parse the code, use parenthesis to be valid. It’s a bit clearer when you see that this is also valid:
(1.).toString()
However with just 1.toString()
it’s trying to parse as a number with a decimal, and it fails.