Odd numbers are whole numbers it cannot be divided exactly into pairs. Odd numbers, when divided by 2, leave a remainder of 1, 3, 5, 7, 9, 11, 13, 15 … are sequential odd numbers. Any integer (not a fraction) that cannot be divided exactly by 2. The last digit is 1, 3, 5, 7 or 9 are the odd numbers.