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  1. #include <stdio.h>
  2. #include <math.h>
  3.  
  4. int main() {
  5.     int num, i, is_prime = 1;
  6.  
  7.     // Asking user to input a number
  8.     printf("Enter a positive integer: ");
  9.     scanf("%d", &num);
  10.  
  11.     if (num <= 1) {
  12.         is_prime = 0; // Numbers less than or equal to 1 are not prime
  13.     } else {
  14.         // Loop to check divisibility
  15.         for (i = 2; i <= sqrt(num); i++) {
  16.             if (num % i == 0) {
  17.                 is_prime = 0; // If divisible, not prime
  18.                 break;
  19.             }
  20.         }
  21.     }
  22.  
  23.     if (is_prime) {
  24.         printf("%d is a prime number.\n", num);
  25.     } else {
  26.         printf("%d is not a prime number.\n", num);
  27.     }
  28.  
  29.     return 0;
  30. }
Success #stdin #stdout 0s 5276KB
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stdin
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Standard input is empty
stdout
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Enter a positive integer: 32765 is not a prime number.
https://ideone.com/i5Bv3m
language:
C (gcc 8.3)
created:
4 days ago
visibility:
public

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