Google Authenticator - Google Authenticator is a multifactor app for mobile devices.

Anki - Anki is a program which makes remembering things easy. Because it's a lot more efficient than traditional study methods, you can either greatly decrease your time spent studying, or greatly increase the amount you learn.

andOTP - andOTP is a two-factor authentication App for Android 4.4+

Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.

Microsoft Authenticator - One app to quickly and securely verify your identity online, for all of your accounts.

Memrise - Learn a new language with games, humorous chatbots and over 30,000 native speaker videos.