Guru Nanak is not a Prophet.

"As far as the teaching in Punjab among the Sikhs is concerned, the friends should obviously avoid disputation with the beliefs of the people, who believe that Guru Nanak was a Prophet. Guru Nanak was indeed a saintly character who was inspired to reconcile the religions of Hinduism and Islam, the followers of which religions had been in violent conflict. The world has seen many such well-intentioned reformers, who have derived their inspiration from the religions of God, without themselves being Prophets."

UHJ 1985.10.27 (Obtained from the NSA of India by Badi Villar for his master's thesis)