Saraveca language

Saraveca is an extinct Arawakan language once spoken in Bolivia by the Sarave. It is said^[1][2] to be the only language with a numeral system based exclusively on five, though in fact quinary systems are not uncommon. To some extent this is also an areal feature of other South American languages; many form their numbers 6–9 as "five + one", "five + two" and so on.

References

1. ^ David Wells, The Penguin Dictionary of Curious and Interesting Numbers", ISBN 0-14-026149-4
2. ^ Encyclopædia Britannica, "Numerals and numeral systems".