ThisNumber is an international directory of phone books and U.S. phone number lookup service.
Very easy to use and free.
Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.
WhosCall - WhosCall is a reliable caller ID app whose popularity has led to its adoption by many users including international media. You can now manage the numbers calling you regardless of whether they are part of your contact list or not... read more.
NoPhoneSpam - Block calls from annoying or private numbers on your Android device. By bitfire.
CallerSmart - CallerSmart is an application that is basically used for the purpose of looking up mystery phone numbers for free.
Should I Answer? - See what phone numbers are most searched and find ratings and users reviews.
Sync.ME - Search over 1 Billion phone numbers worldwide. Identify unknown phone numbers and block unwanted calls.