If your data always looks like this:
123 Main St.
Then the number formula would be:
left({AddressField},instr({AddressField}," ") - 1)
And the street formula would be:
mid({AddressField},instr({AddressField}," ") + 1)
The Instr function returns the numeric position of the first instance of a character or characters within a string, which in your case would be the space between the number and street.
However, I suspect that once you get this working you'll encounter some addresses that don't cooperate, so this will only be the first step.