# Program to find the LCM of two prime numbers

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 = 7Output:21Explanation:

The least numbers greater than equals to 3 and 7 which is a multiple of 3 and 7 is 21.Attention reader! Don’t stop learning now. Get hold of all the important mathematical concepts for competitive programming with the

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Input:N = 5, M = 5Output:5Explanation:

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: .

Since the GCD two different prime numbers are 1, Therefore , 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)*