Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
impertinent [ɪmˈpəːtɪnənt] adj (pupil, question) де́рзкий*де́рзок , наха́льный*наха́лен
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: