sure it can do all that but ask yourself this,
would you download a propper huge (100mb+) calculator that will only run on (a small handful of) the very latest and most powerful devices at a really low framerate, even if it did look bling?
I see what your getting at tegleg, and youāre right, but then again for personal use on a desktop machine, having a huge resource hungry app is actually preferable to me 
Iād much rather explorer.exe actually use more of my GPU, and show me a fully 3D game like environment for managing my files.
or a calc app that had the backend apiās connected to wolfram alpha,
or indeed a notepad that was fully customizable with fancy transitions and animation.
I guess its down to if you are trying to make money, or just make something for yourself.
Then itās better you make your own custom engine for that since UE4 is full of code that is not needed for a calculator.
Do a webgl calculator instead.
Yes and it would be EPIC
The question shouldnāt be āCan I makeā¦ā, but āShould I makeā¦ā Just because something CAN be done, does not mean it SHOULD be done. UE4 seems like waaaay overkill for a calculator, or any ohter utility type mobile app. There are far better and more efficient solutions for something like that.
can i make a chemistry app in which i ad one element and another element to form a third element and if i can add more then 2 element to form the third element!!
In software development, the question of ācan youā¦ā is usually followed with āyesā