Shorcut to know either Number is Prime or not ?

WHAT ARE THE PRIME NUMBERS ?

A Natural number larger than unity is a Prime number if it does not have other divisor except or itself and unity .

PROPERTIES OF THE PRIME NUMBERS

• The lowest Prime Number is  2.

• 2 is also the only even prime number.

• The Lowest odd Prime Number is 3.

CHECK THE NUMBER , IT IS PRIME OR NOT ?

Let we have a number N, we check whether the N is Prime or no

Step 1

Take the Square root of the number. 

Step 2

 Now round off the square root to the immediately lower integer .say it as M.

 Step 3

Now Check the Divisibility of N with all PRIME numbers which are below then M

EXAMPLE

Let the NUMBER is 239.

we know that:-

Square of 15=225
Square of 16=256

so the value of M for this case is 15.

so prime number less then 15 are 2,3,5,7,11 and 13.

If you divide 239 from these Prime Numbers you have reminder . It means the number is Prime Number.