There are some developed sites that use numbers for words, but I don't think I'd so so unless I also had the spelled out version. If I used come2eat, I would also want to have ComeToEat parked on top of it.
Numbers in a domain with a purpose can be good. 1-800 and 24-7 domains come to mind, and anyone would know that 4x4.tld would be valuable for a car site. Pure number domains have value, but unless they mean something are hard to remember. 2020.com would be a super name for an optometrist, and 1250.com might be a good domain for a building at 1250 something street.