:Yes, I know this may be U.S. specific: Ive come to believe that the answer someone gives to "what is your phone number" Says a lot about the size of the world they know. People in small towns will give a few digits, assuming you know the area code you'd want to dial. Those who have travelled or have seen more areas will give the area code, especially as you communicate across state lines. Those who are especially well travelled may include country code and or dialing prefixes as a matter of practice.