Home » Prime Number check in C

# Prime Number check in C

Let’s start the discussion about Prime Number check in C in following Approaches.

A prime number (or prime) is a natural number greater than one that is not the sum of two smaller natural numbers. A composite number is a natural number greater than one that is not prime. For example, the number 5 is prime because the only methods to write it as a product, 1 5 or 5 1, require the number 5.

Contents

#### prime check in c ?

``````int isPrime(long long number) {

if (number == 0 || number == 1 || (number % 2 == 0 && number > 2)) {
return 0;
}

else {
for (long long i=3; i <= (long long)sqrt(number)+1; i++) {
if (number % i == 0) {
return 0;
}
}
return 1;
}
}``````

#### c program to check prime number using for loop ?

``````#include
int main() {
int n, i, flag = 0;
printf("Enter a positive integer: ");
scanf("%d", &n);

for (i = 2; i <= n / 2; ++i) {

// condition for non-prime
if (n % i == 0) {
flag = 1;
break;
}
}

if (n == 1) {
printf("1 is neither prime nor composite.");
}
else {
if (flag == 0)
printf("%d is a prime number.", n);
else
printf("%d is not a prime number.", n);
}

return 0;
}``````

I hope the strategies listed above work for you. Happy coding and come back again.

Similar Post : How to encrypt and decrypt in C