byjus.com › maths › odd-numbersOdd Numbers (Definition, Chart, Properties & Solved Examples) In other words, numbers in the form of 2k+1, where k ∈ Z (i.e. integers) are called odd numbers. It should be noted that numbers or sets of integers on a number line can either be odd or even. Odd Numbers and Even Numbers. The numbers that are not odd, are even numbers, which are divisible by 2.