Is there any way i can grow taller if i'm a guy and am 21 years old?

Unlikely: If you are a healthy male who has completed puberty then it is unlikely that you will grow signficantly taller. Maintain good posture to help make the most of your height. If you entered puberty quite late you may still grow.

You could check: Any further height would depend on having open growth centers in your long bones.A single x-ray of your wrist/hand can be examined for open growth centers. If they have closed, like they do for most males by 18, you are done.