What is the greatest name of Allah agreed upon by researchers, and was it known only to the Prophet, peace and blessings be upon him, and his Household?

Scholars have differed regarding the exact name of Allah, the Most Great (al-Ism al-A'dham). The preponderant opinion is that it is among Allah's Beautiful Names, but it is not known with certainty. The secret behind its concealment lies in encouraging the supplicant to invoke Allah with all His Beautiful Names, thereby attaining the virtue of supplicating with all of them. There is no authentic proof to confirm that any member of the Prophet's household (peace be upon him) was specifically granted knowledge of the Most Great Name.