Early Quenya
otsokainen
cardinal. seventy
okkainen
cardinal. seventy
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
The Early Qenya Grammar (EQG) of the 1920s had ᴱQ. otsokainen “seventy” as a combination of ᴱQ. otso “seven” and ᴱQ. kainen “ten” (PE14/49, 83).
Neo-Quenya: Late in Tolkien’s life, Tolkien changed the Quenya word for “ten” to quëan or quain, which has been the basis for various neologisms for “seventy”: ᴺQ. otoquëan or ᴺQ. otoquain. I prefer to use ᴺQ. otoquain for purposes of Neo-Quenya.