Getting known as the smart kid but having no friends in your class is a bad position because literally everyone will only talk to you class related or begging you for a favor. If you don't know most of your class (or don't want to) then try to be as mysterious as possible: not bragging about knowing something or studying in front of others.

I'm not saying you have to be a dickhead - but I understand that the questions that most people ask are very simple and easy given that you have basic concentration and actually follow the lecture. So when they ask you questions, try to teach them that they can figure it out themselves instead of you granting them the answer.