Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!

Qenya 

-rasta

suffix. twelve

A suffix appearing in [ᴹQ.] yurasta “twenty four” in notes from the 1930s, probably meaning “✱double twelve” (PE14/17 note #6). Thus -rasta means “twelve”, as further evidenced by ᴹ√rasat “twelve” on the same page. This word seems to be the basis for a duodecimal numbering system, with -rasta taking the same role as -cainen “ten”; compare yucainen “twenty” = “✱double ten”. Presumably there are larger numbers like ✱nelerasta “thirty six = triple twelve” and ✱cantarasta “forty eight = quadruple twelve”, the duodecimal equivalents of thirty, forty, etc.