How to Check Whether a Number is Prime or Not, Quantitative Aptitude Study techniques in Number Systems in Competitive Exams
In various competitive exams like CGL, CHSL, JE conducted by SSC and Exams conducted by UPSC and PSC will ask questions like Check whether the given number is prime or not. Checking whether a number is prime or not is really simple if you know this trick. So that you can solve this within a minute, if you practiced well.
Prime numbers are 3,5,7,11,13,17,19 etc. If you want to check whether 349 is prime number or not, if you don't know the trick you will definitely waste your time in competitive exams.
Before checking whether a number is prime or not, you have to study the divisibility of a number by prime numbers like 3,5,7,11,17 etc. If you don't know how to check divisibility of a number, Read on How to Check Divisibility of a Number.
Steps to follow to check a number is Prime or Not
We can study the method using a number say 349
- Find the square root of the Number
√349 ≈ 19 - Find prime numbers below the square root of the number
Prime numbers below 19 are {3,5,7,11,13,17} - Check the divisibility of the given number with the above prime numbers
We have to check divisibility of 349 with {3,5,7,11,13,17,}
Divisibility by 3 - Not divisible
Divisibility by 4 - Not Divisible
Divisibility by 5 - Not Divisible
Divisibility by 6 - Not Divisible
Divisibility by 7 - Not Divisible
Divisibility by 11 - Not Divisible
Divisibility by 13 - Not Divisible
Divisibility by 17 - Not Divisible - If the number is not divisible by any of the prime number mentioned above the number is a prime number
349 is a Prime Number - If the number is divisible by any of these prime numbers the given number is not a prime number
If you know how to check the divisibility of a number quickly, you can definitely score in this section easily. This method includes only simple steps and basic mathematics like square root, divisibility check etc. If you are still having any doubts ask it in the comment section.
If you have any doubts regarding divisibility of a number please feel free to ask through the commenting system
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