Been there, done that, he'll get over it eventually, and at least you're safe in the knowledge that you didn't lead him on intentionally.
I have male friends who I'll happily chat to until the early hours of the morning, but there's nothing romantic there at all, purely having a fun conversation, usually ranting about politics or the falling quality of Doctor Who, they know this, I know this, it's well established. Giving a guy your number can be a sign you like them, but generally when it's a complete stranger. With one guy I know, I asked for his number when we were chatting on facebook because I had to go offline but he was going through a rough time and I wanted to help him out, I didn't mean it in a romantic way. But it kinda went wrong. We're ok now though, all is well.
So trust me, he'll be upset for a while and ignore you but he'll survive. Anyway, to answer the question more clearly, yes, giving a guy your number can show you're interested in them but it isn't a sure sign that you are, it might just be that you like chatting to them as a friend. These things can be misinterpreted, especially if one or both of you is shy. Sadly there's not a great deal you can do if someone mistakes your friendly actions as something more, but let them down gently and let him deal with it at his own pace.