Division Tricks.

These are some easy tricks you can use to calculate divisors of any given number.

Very helpful for competitive exams.

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i)Number divisible by 1: The easiest. Need not to elaborate.

ii)Number divisible by 2:I bet you know what's an even number is!?

iii)Number divisible by 3: Just add all the digits in the given number. If the sum is divisible by 3 then the given number can be divided by 3 too.

eg. For the number 123456. Sum of the digits are 1+2+3+4+5+6=21 it's divisible by 3 hence the given number is divisible by 3.

(Same goes with 9, if the sum is divisible by 9 )

iv)Number divisible by 4: Check the number formed by last two digits. If it's 00 or a number divisible 4 then your number is divisible by 4.

eg. For the number 253154244 , the number formed by last two digits is 44, divisible by 4 hence the given number is divisible by 4.

v)Number divisible by 5: If the last digit is either 0 or 5, the number is divisible by 5.

vi)Number divisible by 6: If the number is divisible by both 2 and 3 it's divisible by 6

( Follow steps ii and iii)

vii)Number divisible by 7: To determine if a number is divisible by 7, take the last digit off the number, double it and subtract the doubled number from the remaining number. If the result is evenly divisible by 7 (e.g. 14, 7, 0, -7, etc.), then the number is divisible by seven. This may need to be repeated several times.

Or,

If you have a 9 digit number, make three numbers taking 3digits at a time from right to left and substruct the sum of the odd ones with the number in the even position.

If it's zero or a multiple of 7 the given number is divisible by 7.

eg. Is the number 264 389 132 divisible by 7?

1. We make three numbers 264,389,132

2. Sum of the numbers in odd position 

= 264+132 = 396

And the number in even position is 389

3. Hence the resulten = 396-389=7

Hence the given number is divisible by 7.

viii)Number divisible by 8: Create a number using last 3 digits if it's divisible by 8, the given number is divisible by 8.

ix)Number divisible by 9: Sum all the digits and form a number. If the resulten is divisible by 9 , the given number is divisible by 9.

x)Number divisible by 10: If it has 0 as the last digit, it's divisible by 10.

xi)Number divisible by 11: Find the sum of all terms in even positions and the sum of all terms in odd position . Substruct the results if it's zero or a multiple of 11, the given number is divisible by 11.

xii)Number divisible by 12: If the number is divisible by both 3 and 4 it's divisible by 12.

xiii)Number divisible by 13:If you have a 9 digit number make three numbers taking 3digits at a time from right to left and substruct the sum of the odd ones with the number in the even position.If it's zero or a multiple of 13 the given number is divisible by 13.

xiv)Number divisible by 14: If the given number is separately divisible by 2 and 7 then it's divisible by 14.

xv)Number divisible by 15: If the given number is separately divisible by 3 and 5 then it's divisible by 15.

xvi)Number divisible by 16: Check the number formed by last three digits. If it's 000 or a number divisible 16 then your number is divisible by 16.

eg. For the number 253154160 , the number formed by last three digits is 160, divisible by 16 hence the given number is divisible by 16.

xvii)Number divisible by 17: Take the last digit and multiply it by 5 and substruct from the remaining number if the resulten is a multiple of 17 , the given number is divisible by 17. This step can be repeated to obtain a moderately easy form of number.

xviii)Number divisible by 18: If the given number is separately divisible by 9 and 2 then it's divisible by 18.

xix)Number divisible by 19:Add two times the last digit to the remaining leading truncated number. If the result is divisible by 19, then so was the first number. Apply this rule over and over again as necessary.

xx)Number divisible by 20: If the number is separately divisible by 4 & 5 then it's divisible by 20.

That's it for now. Will update more division tricks for prime numbers later. Thanks for reading.