Prime number
Prime numbers are those which are only divisible by one and themselves
Example : 13 is prime number
Because
it has only two factors , 1 and 13.
the number two is taken to be the first prime number
The sequence of prime number begins,
2,3,5,7,11,13,17,19,23,29,31..
it is an infinitely long sequence without any repeating pattern.the pattern is unique and there is no known formula for working out all the prime numbers by testing each number to see if it has more than two factor
one remarkable feature of this sequence is that the first prime number 2 is even and the rest are odd
Simple trick to find the given number is prime of not
Example 83 is prime or not
Step 1 find out a number which is perfect square just more than the given number
( just more than the 83 , square number is 100 ..100 is square of 10)
Step 2 Take all prime number below of that number
Take all prime number below 10 its 2,3,5,7,
Step 3 If it is not divisible by this number then this number is prime number
83 is not divisible by 2,3,5 ,7 so 83 is prime number
Example 2 find 109 is prime or not
11 square is just more than 109 so
prime number below 11 is 2,3,5,7,11
109 is not divisible by 2,3,5,7,11 so it is a prime number
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