Divisibility rules of Prime Numbers.

Divisibility Rules of Prime Numbers:-

Prime Numbers are those numbers,which have only two factors 1 and number itself.
Numbers such as:-2,3,5,7,11 are  Prime Numbers.
Divisibility rule of 2:-A number is divisible by 2,if the digit in the ones place is,0,2,4,6 or 8,that is even number.
Ex-12,230 are divisible by 2.
The first number is 12, 2 is in its ones place. It is divisible by 2.
The second number is 230,0 is in its ones place,so the number is divisible by 2.

Divisibility rule of 3:- A number is divisible by 3,if the sum of numbers is divisible by 3.
Ex.132,306.The sum of number is 1+3+2=6,6 is divisible by 3,so the number 132 is divisible by 3.The second number is 306,the sum of number is 3+0+6=9, 9 is divisible by 3,so the number 306 is divisible by 3.

Divisibility rule of 5:-
The number is divisible by 5,if it's ones place has 5 or 0.
Ex-105,210.These numbers are divisible by 5.105 is ended with 5 and 210 is ended with 0,These two numbers are divisible by 5.
Divisible by 7:- A number is divisible by 7,if the sum of three times the digit in the tens place and the digit in the ones place is divisible by 7.
Take the number 84. 8*3+4=28. 28 is divisible by 7. So the number is divisible by 7.
A number of 3 or more digit is divisible by 7, If the sum of number,which are in tens and ones place and twice the remaining number is divisible by 7.
455- 55+2*4= 63, 63 is divisible by 7, so the number 455 is divisible by 7.
Divisible by 11:-A number is divisible 11, if the difference of sum of digits in the even places,and sum of the digits in the odd places is 0 or multiple of 11.
Take the number 13123- The sum of the digits in even places is 3+2=5
The sum of digit in the odd places is 1+1+3=5. The difference is 5-5=0.
This number is divisible by 11.


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