There are 9 13-letter words that end with 'um'.
| armamentarium | chrysanthemum |
| decamethonium | hexamethonium |
| mycobacterium | odontoglossum |
| rutherfordium | perichondrium |
| zoosporangium | |
Note: These 9 13-letter words that end with 'um' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words end with ium, lum, rum, tum, num, eum, cum, dum, sum, gum, mum, bum, kum, uum, aum, hum, oum, vum, wum, jum, pum, yum.
3-letter words end with 'um' (10)