number9Pronunciation of the number 9. 9 (nine) is the Arabic number which comes after 8 and before 10. It is an odd number, and is the hhest single-dit number. It is also a square number. In RomanYour guide to the number 9, an odd composite number composed of a single prime multiplied by itself. Mathematical info, prime factorization, fun facts and numerical data for STEM, education and fun.