Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.
Standard Notes - A safe place for your notes, thoughts, and life's work
CallApp - Free Caller ID & Call Blocker app that allows mobile users to block phone calls, identify calls, blacklist unwanted callers and much more.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
CallerSmart - CallerSmart is an application that is basically used for the purpose of looking up mystery phone numbers for free.