C Exercises: Find largest prime factor of 438927456

Last update on August 09 2025 12:46:59 (UTC/GMT +8 hours)

19. Largest Prime Factor Variants

The prime factors of 13195 are 5, 7, 13, 29.
Write a C program to find the largest prime factor of the number 438927456.

C Code:

#include <stdio.h>
int main(void)
{
  unsigned long long n = 438927456L;
  unsigned long long i;
  for (i = 2ULL; i < n; i++) {
  	//1ULL is 'unsigned long long
    while (n % i == 0) {
      n /= i;
    }
  }
  printf("%llu\n", n);
  return 0;
}

Sample Output:

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to find the largest prime factor of a number using trial division with optimizations.
Write a C program to compute the largest prime factor recursively.
Write a C program to list all prime factors of a number and highlight the largest.
Write a C program to find the largest prime factor using a sieve method for enhanced performance.

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