It was probably someone you know using Google's new "Call phones from Gmail" service. You should try it. Or next time somebody calls you from that number, pick it up. It may be a long lost friend, or better.
You don't have to take my word for it; there are several other websites confirming the same thing. I'm sure there will be other phone numbers used, but on two separate calls (one to a landline, and one to a cell phone) used the same incoming number.
Other sites that verify the phone number coming from Google: