Im 17 about to turn 18 and I can vouge for the fact that for the guys (even though Im a girl) that are my age have just about one thing on their mind, at least for the majority of guys I know. When your my age, your not really looking to settle down, its suppose to be the time of your life, go out, have fun, party, and have sex. Thats simply what this world has come to for us in our later teen years.
I suggest that you take a chance to get to know him, figure out what his real age is, and make him ask for your number. If you give your number to him without asking, that may make you appear to be rather easy in his eyes, depending on what kind of a guy he is. He may look at that number as an easy booty call, will call you, ask you out on a date, try to do something with you and if your not willing, you wont hear from him again.
Just be careful...especially with the small age gap as well....the law comes into play eventually.