What is the greatest composite odd numbers less than 40

The greatest composite odd number less than 40 is 39

A composite number is divisible by something other than 1 and itself, and the number we are looking for is odd and less than 40. 39 fits all of these because it is less than 40 and odd. Also, you can divide it by 3 and 13, meaning that it is composite. So, the answer is 39.