Art, I think the plectrum (and 5 string) has 22 frets. The tenor mostly comes in 19 and 17 fret versions, the 17 fret being popular with the Irish style players because of the lesser stretch involved for the open melody playing. I say mostly as I am in some doubt as I have for example read references to things like 18 fret tenors but 19 and 17 are the "standards".

Jon