TESTS OF DIVISIBILITY
(a) Divisibility By 2 :
A number is divisible by 2 if its unit digit is divisible by 2 .
Example : (1). 7684
Solution:
The unit is 4 , which is divisible by 2 (4÷2=2)  so 7684 is divisible by 2.
(2). 2785
Solution : The unit digit is 5 , which is not divisible by 2 . so 2785 is never divisible by 2.

(b). Divisibility by 3 :
A number is divisible by 3 only when the sum of its digit is divisible by 3.
Example : (1). 695421
Solution ; in the number 695421 , the sum of the digit is 27 , which is divisible by 3.
So the number is divisible by 3 .
(2). 948655
Solution : in the number 948655 , the sum of the digits is 37 , which is not divisible by 3 .
So the number 948655 is not divisible by 3 .

(c). Divisibility by 9 :
A number is divisible by 9 only when the sum of its digits is divisible by 9 .
Example : (1). 246591
In the number 246591 the sum of its digits
= 27 , which is divisible by 9.
So the number is divisible by 9 .

(d) . Divisibility by 4 : A number is divisible by  4 if the number  formed by its last two digits is divisible by 4 .
Example : (1) 6879376
Solution : since 76 {the last two digit} is divisible by 4 . so the number 6879376 is divisible by 4 .

(e). Divisibility by 8 : A number is divisible by 8 if the number formed by hundred's ten's and unit's digit of the given number is divisible by 8  .
Example : (1) 16789352 , the number formed by last three digits , namely 352 is divisible by 8. So 16789352 is divisible by 8 .