Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.
Numverify - Global phone number validation and lookup API
PhoneGenerator.net - Generate random phone numbers for all countries using the mobile phone generator. These numbers are fake, but they are built using the validations of telephone numbers.
Antideo - Email, IP address and phone number validation API service
CallerSmart - CallerSmart is an application that is basically used for the purpose of looking up mystery phone numbers for free.
RealValidito - Phone Validator | Free Phone Number Validation & Phone Number Lookup Service | Realvalidito