Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.
Should I Answer? - See what phone numbers are most searched and find ratings and users reviews.
CallerSmart - CallerSmart is an application that is basically used for the purpose of looking up mystery phone numbers for free.
Nomorobo - Nomorobo blocks annoying robocalls, telemarketers, and phone scams.
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.