Distinct Prime Factors of a given number N

Last Updated : 23 Jul, 2025

Given a number N, the task is to find the distinct Prime Factors of N.

Examples:

Input: N = 12
Output: 2 3
Explanation: The factors of 12 are 1, 2, 3, 4, 6, 12.
Among these the distinct prime factors are 2 and 3.

Input: N = 39
Output: 3 13

Approach: The approach is to use a map to check whether a given factor of the number has occurred earlier or not. Now follow the below steps to solve this problem:

  1. Create a map visited to keep track of all previous prime factors.
  2. Create a variable C, and initialize it with 2.
  3. While N is divisible by C, print C if C is not present in the map. Now divide N by C. Also increment C by 1.

Below is the implementation of the above approach:

C++
// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;

// Function to find distinct prime factor
// of a number N
void distinctPrimeFactors(int N)
{
    if (N < 2) {
        cout << -1;
    }

    int c = 2;
    unordered_map<int, bool> visited;

    while (N > 1) {
        if (N % c == 0) {
            if (!visited[c]) {
                cout << c << " ";
                visited[c] = 1;
            }
            N /= c;
        }
        else
            c++;
    }
}

// Driver Code
int main()
{
    int N = 39;
    distinctPrimeFactors(N);
    return 0;
}
Java
// Java program for the above approach
import java.util.*;
public class GFG
{

  // Function to find distinct prime factor
  // of a number N
  static void distinctPrimeFactors(int N)
  {
    if (N < 2) {
      System.out.print(-1);
    }

    int c = 2;

    // Create a new dictionary of
    // strings, with string keys.
    HashMap<Integer, Boolean> visited = new HashMap<>();

    for(int i = 0; i < N; i++) {
      visited.put(i, false);
    }

    while (N > 1) {
      if (N % c == 0) {
        if(visited.containsKey(c)){
          if (!visited.get(c)) {
            System.out.print(c + " ");
            visited.put(c, true);
          }
        }
        N /= c;
      }
      else
        c++;
    }
  }

  // Driver Code
  public static void main(String[] args)
  {
    int N = 39;
    distinctPrimeFactors(N);
  }
}

// This code is contributed by Samim Hossain Mondal
Python3
# python3 program for the above approach

# Function to find distinct prime factor
# of a number N
def distinctPrimeFactors(N):

    if (N < 2):
        print(-1)

    c = 2
    visited = {}

    while (N > 1):
        if (N % c == 0):
            if (not c in visited):
                print(c, end=" ")
                visited[c] = 1 if c in visited else 0

            N //= c

        else:
            c += 1

# Driver Code
if __name__ == "__main__":

    N = 39
    distinctPrimeFactors(N)

# This code is contributed by rakeshsahni
C#
// C# program for the above approach
using System;
using System.Collections.Generic;

class GFG
{

  // Function to find distinct prime factor
  // of a number N
  static void distinctPrimeFactors(int N)
  {
    if (N < 2) {
      Console.Write(-1);
    }

    int c = 2;

    // Create a new dictionary of
    // strings, with string keys.
    Dictionary<int, bool> visited =
      new Dictionary<int, bool>();

    for(int i = 0; i < N; i++) {
      visited[i] = false;
    }

    while (N > 1) {
      if (N % c == 0) {
        if(visited.ContainsKey(c)){
          if (!visited[c]) {
            Console.Write(c + " ");
            visited[c] = true;
          }
        }
        N /= c;
      }
      else
        c++;
    }
  }

  // Driver Code
  public static void Main()
  {
    int N = 39;
    distinctPrimeFactors(N);
  }
}

// This code is contributed by Samim Hossain Mondal.
JavaScript
<script>
    // JavaScript program for the above approach

    // Function to find distinct prime factor
    // of a number N
    const distinctPrimeFactors = (N) => {
        if (N < 2) {
            document.write(-1);
        }

        let c = 2;
        let visited = {};

        while (N > 1) {
            if (N % c == 0) {
                if (!(c in visited)) {
                    document.write(`${c} `);
                    visited[c] = 1;
                }
                N = parseInt(N / c);
            }
            else
                c++;
        }
    }

    // Driver Code

    let N = 39;
    distinctPrimeFactors(N);

// This code is contributed by rakeshsahni

</script>

Output
3 13

Time Complexity: O(N)
Auxiliary Space: O(N1/2)


Efficient Approach: This approach is similar to above approach where we find prime factors. The only difference is that we traverse from 2 to sqrt(n) to find all prime factors since we know that is sufficient for checking for prime numbers as well. If the number is still found to be greater than 2 then it is prime and we need to print it as well.

C++14
// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;

// Function to find distinct prime factor
// of a number N
void distinctPrimeFactors(int N)
{
    if (N < 2) {
        cout << -1;
        return;
    }
    if (N == 2) {
        cout << 2;
        return;
    }

    unordered_map<int, bool> visited;

    for (int i = 2; i * i <= N; i++) {
        while (N % i == 0) {
            if (!visited[i]) {
                cout << i << " ";
                visited[i] = 1;
            }
            N /= i;
        }
    }
    if (N > 2)
        cout << N;
}

// Driver Code
int main()
{
    int N = 315;
    distinctPrimeFactors(N);
    return 0;
}
Java
// Java program for the above approach
import java.util.*;
class GFG 
{
  // Function to find distinct prime factor
  // of a number N
  static void distinctPrimeFactors(int N)
  {
    if (N < 2) {
      System.out.print(-1);
      return;
    }
    if (N == 2) {
      System.out.print(2);
      return;
    }
    HashMap<Integer, Boolean> visited = new HashMap<>();
    for (int i = 2; i * i <= N; i++) {
      while (N % i == 0) {
        if (!visited.containsKey(i)) {
          System.out.print(i + " ");
          visited.put(i, true);
        }
        N /= i;
      }
    }
    if (N > 2) {
      System.out.print(N);
    }
  }

  // Driver Code
  public static void main(String[] args)
  {
    int N = 315;
    distinctPrimeFactors(N);
  }
}

// This code is contributed by Taranpreet
Python3
# Python program for the above approach

# Function to find distinct prime factor
# of a number N
def distinctPrimeFactors(N):
    
    if (N < 2):
        print(-1)
        return
    if N == 2:
      print(2)
      return
    visited = {}
    
    i = 2
    while(i * i <= N):
        while(N % i == 0):
            if(i not in visited):
                print(i , end = " ")
                visited[i] = 1
                
            N //= i
        i+=1
            
    if(N > 2):
        print(N)

# Driver Code
N = 315
distinctPrimeFactors(N);

# This code is contributed by Shubham Singh
C#
// C# program for the above approach
using System;
using System.Collections.Generic;

class GFG
{
  
  // Function to find distinct prime factor
  // of a number N
  static void distinctPrimeFactors(int N)
  {
    if (N < 2) {
      Console.Write(-1);
      return;
    }
    if (N == 2) {
      Console.Write(2);
      return;
    }
    Dictionary<int, bool> visited =
      new Dictionary<int, bool>();

    for (int i = 2; i * i <= N; i++) {
      while (N % i == 0) {
        if (!visited.ContainsKey(i)) {
          Console.Write(i + " ");
          visited[i] =  true;
        }
        N /= i;
      }
    }
    if (N > 2) {
      Console.Write(N);
    }
  }
      
  // Driver code
  public static void Main()
  {
    int N = 315;
    distinctPrimeFactors(N);
  }
}

// This code is contributed by avijitmondal1998
JavaScript
<script>
// Javascript program for the above approach

// Function to find distinct prime factor
// of a number N
function distinctPrimeFactors(N)
{
    if (N < 2) {
        document.write(-1);
        return;
    }
    
    if (N === 2) {
        document.write(2);
        return;
    }
    visited = {};
    
    for(var i = 2; i * i <= N; i++)
    {
        while(N % i == 0)
        {
            if(!visited[i])
            {
                document.write(i + " ");
                visited[i] = 1;
            }
            N /= i;
        }
    }
    if(N > 2)
    document.write(N);
}

// Driver Code
var N = 315;
distinctPrimeFactors(N);

// This code is contributed by Shubham Singh
</script>

Output
3 5 7

Time Complexity: O(N^(1/2))
Auxiliary Space: O(N^(1/2))

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