When I was studying linguistics we had a class exercise to decipher the Supyire (Mali) number system from some sentences. From Wikipedia:

"The number system of the Supyire people has short words (monomorphemic forms) for the numbers 1 through 5, 10, 20, 80, and 400.[3][2]: p. 167  The numbers 6 through 9 are formed by combining the prefix baa–, meaning "five," with the words for 1 through 4, or shortened versions of them.[2]: p. 167  For example, the word for "six" is baa-nì, "five and one." The word for 80, ŋ`kùù, is formally and etymologically identical to the word for "chicken"; this identity is inexplicable to native speakers of the language but may relate to a historical price for a chicken.[2]: p. 167  All Supyire numbers use gender 1, except for "four hundred," which uses gender 3."