Should I Answer? - See what phone numbers are most searched and find ratings and users reviews.
Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.
CallApp - Free Caller ID & Call Blocker app that allows mobile users to block phone calls, identify calls, blacklist unwanted callers and much more.
Nomorobo - Nomorobo blocks annoying robocalls, telemarketers, and phone scams.
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.