how can i find out whose phone number this is
If you have a phone number and not a name, you can do a reverse number search on the white pages website. This only works if the phone number is a landline and lis listed in the directory. This is the link: http://www.whitepages.com/
Doing reverse phone lookup at http://goo.gl/69HKVA can help you to find out who belongs a phone number.