# What Are Odd Numbers? (Mathematics Lesson)

# What Are Odd Numbers?

Odd numbers are integers that cannot be divided exactly by 2.# How to Check if a Number Is an Odd Number

**Question**: Is 25 an odd number?

Step 1

25 ÷ 2 = 12.5.

Step 2

**Step 1**is a whole number, the original number is even. Else it is odd.

12.5 is not a whole number. 25 is an odd number.

# Real Examples of Odd Numbers

Some examples of odd numbers are:##### Quick Test

**show**

##### Note

# FORMAL DEFINITION OF ODD NUMBERS

A number n is odd if there exists an integer k, such that:This means than n can never be divided exactly by 2 - if it is divided by 2 there will always be a remainder of 1.

**A QUICK WAY TO CHECK IF A NUMBER IS AN ODD NUMBER**

A number is odd if its last digit is 1, 3, 5, 7 or 9.