# C Program to Find Sum of All Prime Numbers Between 1 to N

• Write a C program to print all prime numbers between 1 to N using for loop.
• Wap in C to print prime numbers between 1 to 100.

#### Required Knowledge

A Prime number is a natural number greater than 1 that is only divisible by either 1 or itself. Here is the list of first few prime numbers
2 3 5 7 11 13 17 19 23....

Algorithm to check whether a number is prime number or not
Let, N be a positive number.
• For every number i, between 2 to N/2(2<= i <= N/2) check whether i divides N completely(check If i is a factor of N).
• if (N % i == 0), then N cannot be a Prime number.
• If none of the number between 2 to N/2 divides N completely then N is a prime number.

## C program to print sum of all prime numbers between 1 to N

```#include <stdio.h>

int main() {
int counter, N, i, isPrime, primeFactorSum = 0;
/*
* Take a number as input from user
*/
printf("Enter a Number\n");
scanf("%d", &N);

/* Check for every number between 1 to N,
whether it is prime number or not  */
for(counter = 2; counter <= N; counter++) {
isPrime = 1;
for(i = 2; i <=(counter/2); ++i) {
if(counter%i==0) {
isPrime = 0;
break;
}
}

if(isPrime==1)
primeFactorSum += counter;
}

printf("Sum of Prime Numbers between 1 to %d : %d", N,primeFactorSum);
return 0;
}
```

Output
```Enter a Number
15
List of Prime Factors of 15
3 5
```
```Enter a Number
50
List of Prime Factors of 50
2 5
```

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