Divisibility rules are quick ways to decide if one number can be divided evenly by another number—without doing long division. They help you find factors, simplify fractions, and recognize number patterns.
If a number divides evenly (with no remainder), it is said to be “divisible” by that number.
A number is divisible by 2 if it is an even number.
All even numbers are divisible by 2.
A number is divisible by 3 if the sum of its digits is divisible by 3.
This rule works for any size number—just keep adding the digits until you can tell if it’s divisible by 3.
A number is divisible by 4 if the number formed by its last two digits is divisible by 4.
All numbers ending in 00, 04, 08, 12, 16, 20, and so on are divisible by 4.
A number is divisible by 5 if its last digit is 0 or 5.
Every number that ends in 0 or 5 has 5 as a factor.
A number is divisible by 6 if it is divisible by both 2 and 3.
This rule combines two smaller rules—if both conditions are true, the number is divisible by 6.
A number is divisible by 8 if the last three digits of the number form a number that is divisible by 8.
For smaller numbers (less than 1,000), you can directly check if the number itself is divisible by 8.
A number is divisible by 9 if the sum of its digits is divisible by 9.
The divisibility rules for 3 and 9 are similar—9’s rule is just a stronger version of 3’s rule.
A number is divisible by 10 if it ends in 0.
Every multiple of 10 ends in zero. This rule is the easiest one to remember!
Divisibility rules make it easier to find factors, simplify fractions, and check if numbers are prime or composite without dividing.
Mastering these rules will help you solve math problems faster and with greater confidence.