If you're trying to figure out if a number is divisible by another, you'll need to know the Divisibility Rules. The numbers 2 to 20 are used for the divisibility tests. It helps in the discovery of integer factors and multiples without the need for time-consuming division procedures. It is possible to find out whether a number is divisible by applying divisibility rules mentally. Divisibility tests will be explained in detail in this blog post.

Rules of Divisibility for the Number 7:

The rule for 7 divisibility is a little complex, however, the steps listed below will help you understand it:

Take the number's final digit out and make it double. 

Take the number's final digit out and make it double.  Subtraction of the double number from the remaining number.

The resultant number is divisible by 7 or if it is zero or the easily topicIdentifiable two-digit multiple of 7.

If this doesn't work, try it again.

Example:

Let’s constopicIder the number 2407.

Start by removing the last digit. In our case, it is 7.

Now, you have to double the last digit: 7 x 2 = 14.

You have to subtract the number 14 from the remaining digits 240.

240 – 14 = 226

Now again you have to repeat the process and remove the last digit of 226. That is 6. The next step is to double the removed last digit: 6 x 2 = 12. You have to subtract the number 12 from the remaining digits 22.

22 – 12 = 10

As 10 is not divisible by 7, 2407 is also not divisible by 7.

Divisibility Rule for the number 8:

The Divisibility Rule of 8 states that to determine whether a number is divisible by 8, you must look at the final three digits of the number.

Example:

Let us constopicIder the number 2856

You would notice that the last three digits are 856

As, 856 is completely divisible by 8, so the original number 2856 is also divisible by 8.

Divisibility Rule for the number 9:

As with divisibility by 3, the rule for divisibility by 9 is quite similar. If the original number's sum of digits is divisible by 9, the number is divisible by 9.

Example:

Suppose you are given the number 3199.

The sum of digits are 3 + 1 + 9 + 9 = 22

22 is not divisible by 9, so 3199 is also not divisible by 9.