Charles Ellicott Commentary 2 Chronicles 33:21

"Amon was twenty and two years old when he began to reign; and he reigned two years in Jerusalem." — 2 Chronicles 33:21 (ASV)

THE REIGN OF AMON (2 Chronicles 33:21–25. Compare to 2 Kings 21:19–26).

Amon was two and twenty years old. —So 2 Kings 21:19, which adds his mother’s name and parentage.