What is an odd number? 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 winning numbers usually include some odd and some even numbers, so it is generally 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 Gold. In some cases, it may be helpful to play more odd or more even numbers than usual, so Smart Luck lotto software can help you play the game smarter.