Hi.

There are millions of apps for android on Play Store and you are free to use any of them if they serve your purpose. There are no exclusive apps that a CSE student should have. It all depends on your usage and area of interest. However, you could try getting a scientific calculator app, RealCalc (also a physical one because you will need it for sure), Apps related to MOOC Courses like Coursera, if you are inclined towards coding then apps such as Enki App, CodeHub, Encode, Mimo etc.

I hope this helps.

Good Luck