He's clearly interested in you if he asks for your number. I'm not sure if he likes you as in he has a crush on you, but he definitely wants to be friends at the very least. And when you approach him, just be casual. Don't be all awkward because you didn't do anything wrong...unless you just told him no without explaining that you don't have a phone. If you just told him no, I think you should explain to him why. He should at least know that. What happens after that is up to him.