A simplistic but nice application for Android I found looking for this after reading parent's comment. https://play.google.com/store/apps/details?id=us.mathlab.

A simplistic but nice application for Android I found looking for this after reading parent's comment. https://play.google.com/store/apps/details?id=us.mathlab.android https://play.google.com/store/apps/details?id=us.mathlab.and... (Adware/Non-free/closed source)