Can an android phone number and an imessage number be the same?

I was trying to text a friend who has an android phone, and the message went through as an imessage, someone else answered back that I had the wrong number. I checked and I had the right number so I turned imessage off and sent the text again. This time it went through to my friend. Is it possible for someone to have the same number for imessage as someone else has for an android phone?