OT-PROPHET.filter - nkjv twenty-one:

nkjv@Jeremiah:52:1 @ Zedekiah was twenty-one years old when he became king, and he reigned eleven years in Jerusalem. His mother's name was Hamutal the daughter of Jeremiah of Libnah.

nkjv@Daniel:10:13 @ But the prince of the kingdom of Persia withstood me twenty-one days; and behold, Michael, one of the chief princes, came to help me, for I had been left alone there with the kings of Persia.