Good calculator app for android? (phsycis, chemistry, calculus)

I got out of the Navy recently and am finishing up my degree. Its 2016. I don't want to buy a physical calculator. I thought maybe some of you duders would know of a good android app?

I need something that is scientific for calculus, physics, and chemistry. I would love if it had a memory where I could program custom variables.

I always use Wolfram Alpha but there is probably a ton of other ones.