Description:
Saraveca is an extinct Arawakan language once spoken in Bolivia by the Sarave. It is said 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...... full article at Wikipedia