How many movies have Mumtaz Askari and O.P. Nayyar collaborated on?

They have worked on 4 movies together! Their first movie together was Mere Sanam (1965) while their highest rated movie together was Yeh Raat Phir Na Aaygi (1966). They have not worked together since C.I.D. 909 (1967). They are most known for their romance films together.