The number being described is 21. It is a composite, odd number that is not a square number. 21 is a deficient number because the sum of its proper factors (7, 3, and 1) is less than 21. The first five multiples of 21 are 21, 42, 63, 84, and 105. The four factors of 21 are 1, 3, 7, and 21.