Understanding these rules of divisibility will help: v Speed up factorization of numbers and v Solve some of the tricky problems However, it is also important to understand why these rules work. 

Some of the rules are mentioned below. A number is divisible by: 

2 
If the last digit is divisible by 2 
3 
If the sum of digits in the number is divisible by 3 
4 
If the last 2 digits are divisible by 4 
5 
If the last digit is 0 or 5 
6 
If it is divisible by 2 and 3 
7 
Complicated : we will discuss later in the class 
8 
If the last 3 digits are divisible by 8 
9 
If the sum of digits is divisible by 9 
10 
If the last digit is 0 