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Program to find the LCM of two prime numbers

  • Last Updated : 27 Jun, 2021

Given two prime numbers N and M, the task is to find the Least Common Multiple(LCM) of the two given prime numbers.
Examples: 
 

Input: N = 3, M = 7 
Output: 21 
Explanation: 
The least numbers greater than equals to 3 and 7 which is a multiple of 3 and 7 is 21.

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Input: N = 5, M = 5 
Output:
Explanation: 
The least numbers greater than equals to 5 and 5 which is a multiple of 5 and 5 is 5. 
 

Approach: As we know that product of two numbers equals to the product of their Greatest Common Divisor(GCD) and Least Common Multiple(LCM). So, the LCM of the two given prime numbers can be given by: LCM(a, b) = \frac{a * b}{GCD(a, b)}      .
Since the GCD two different prime numbers are 1, Therefore LCM(a, b) = a * b      , and if the two given numbers are same then the LCM is the number itself.

Below is the implementation of the above approach: 

C++




// C++ Program to find LCM of two
// prime numbers
#include <bits/stdc++.h>
using namespace std;
 
// Function to return the LCM of two
// prime numbers
int findLCMPrime(int a, int b)
{
    // If the two numbers are equal
    // then return any one of a and b
    if (a == b) {
        return a;
    }
 
    // Else return product of numbers
    return a * b;
}
 
// Driver code
int main()
{
    // Given two numbers
    int a = 3, b = 5;
 
    // Function Call
    cout << findLCMPrime(a, b);
    return 0;
}

Java




// Java Program to find LCM of two
// prime numbers
class GFG{
     
// Function to return the LCM of two
// prime numbers
static int findLCMPrime(int a, int b)
{
    // If the two numbers are equal
    // then return any one of a and b
    if (a == b)
    {
        return a;
    }
 
    // Else return product of numbers
    return a * b;
}
 
// Driver code
public static void main (String[] args)
{
    // Given two numbers
    int a = 3, b = 5;
 
    // Function Call
    System.out.println(findLCMPrime(a, b));
}
}
 
// This code is contributed by AnkitRai01

Python3




# Python3 program to find LCM of two
# prime numbers
 
# Function to return the LCM of two
# prime numbers
def findLCMPrime(a, b):
 
    # If the two numbers are equal
    # then return any one of a and b
    if (a == b):
        return a;
 
    # Else return product of the numbers
    return a * b;
 
# Driver code
if __name__ == "__main__":
 
    # Given two numbers
    a = 3; b = 5;
 
    # Function Call
    print(findLCMPrime(a, b));
 
# This code is contributed by AnkitRai01

C#




// C# program to find LCM of two prime numbers
using System;
 
class GFG{
     
// Function to return the LCM of two
// prime numbers
static int findLCMPrime(int a, int b)
{
     
    // If the two numbers are equal
    // then return any one of a and b
    if (a == b)
    {
        return a;
    }
     
    // Else return product of numbers
    return a * b;
}
     
// Driver code
public static void Main (string[] args)
{
     
    // Given two numbers
    int a = 3, b = 5;
     
    // Function Call
    Console.WriteLine(findLCMPrime(a, b));
}
}
 
// This code is contributed by AnkitRai01

Javascript




<script>
 
// Javascript Program to find LCM of two
// prime numbers
 
// Function to return the LCM of two
// prime numbers
function findLCMPrime(a, b)
{
     
    // If the two numbers are equal
    // then return any one of a and b
    if (a == b)
    {
        return a;
    }
   
    // Else return product of numbers
    return a * b;
}
  
// Driver code
 
// Given two numbers
let a = 3, b = 5;
 
// Function Call
document.write(findLCMPrime(a, b));
  
// This code is contributed by Akshit Saxena
  
</script>
Output
15

Time Complexity: O(1)
Auxiliary Space: O(1)




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