An odd number is an integer that is not a multiple of two. Examples: -7, 1, 15, 43. Odd numbers are the opposite of even numbers. A lotto number must be either odd or even. In a lotto drawing, the set of numbers usually include some odd and some even numbers, so it is good to include some of both when you are playing lotto tickets. To track the odd/even lotto number trend, use the Odd Even Bias Tracker Chart in Advantage Plus.