'Forty one' in the Bible

Now Rehoboam the son of Solomon reigned in Judah. Rehoboam was forty-one years old when he became king, and he reigned seventeen years in Jerusalem, the city the Lord had chosen from all the tribes of Israel in which to put His Name (Presence). His mother’s name was Naamah the Ammonitess.

He reigned forty-one years in Jerusalem. His [great-grand]mother was Maacah the daughter of Abishalom (Absalom).