A Cullen Number is a number of the form is 2^{n} * n + 1 where n is an integer. The first few Cullen numbers are 1, 3, 9, 25, 65, 161, 385, 897, 2049, 4609 . . . . . . **Examples:**

Input : n = 4 Output :65 Input : n = 0 Output : 1 Input : n = 6 Output : 161

Below is implementation of formula. We use bitwise left-shift operator to find 2^{n}, then multiply the result with n and finally returns (1 << n)*n + 1.

## C++

`// C++ program to find Cullen number` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// function to find n'th cullen number` `unsigned findCullen(unsigned n)` `{` ` ` `return` `(1 << n) * n + 1;` `}` `// Driver code` `int` `main()` `{` ` ` `int` `n = 2;` ` ` `cout << findCullen(n);` ` ` `return` `0;` `}` |

## Java

`// Java program to find Cullen number` `import` `java.io.*;` `class` `GFG {` ` ` `// function to find n'th cullen number` ` ` `static` `int` `findCullen(` `int` `n)` ` ` `{` ` ` `return` `(` `1` `<< n) * n + ` `1` `;` ` ` `}` ` ` `// Driver code` ` ` `public` `static` `void` `main(String[] args)` ` ` `{` ` ` `int` `n = ` `2` `;` ` ` `System.out.println(findCullen(n));` ` ` `}` `}` `// This code is contributed by vt_m.` |

## Python3

`# Python program to` `# find Cullen number` `# Function to calculate` `# Cullen number` `def` `findCullen(n):` ` ` `# Formula to calculate` ` ` `# nth Cullen number` ` ` ` ` `return` `(` `1` `<< n) ` `*` `n ` `+` `1` `# Driver Code` `n ` `=` `2` `print` `(findCullen(n))` `# This code is contributed` `# by aj_36 ` |

## C#

`// C# program to find Cullen number` `using` `System;` `class` `GFG {` ` ` `// function to find n'th cullen number` ` ` `static` `int` `findCullen(` `int` `n)` ` ` `{` ` ` `return` `(1 << n) * n + 1;` ` ` `}` ` ` `// Driver code` ` ` `public` `static` `void` `Main()` ` ` `{` ` ` `int` `n = 2;` ` ` `Console.WriteLine(findCullen(n));` ` ` `}` `}` `// This code is contributed by vt_m.` |

## PHP

`<?php` `// PHP program to` `// find Cullen number` `// function to find n'th` `// cullen number` `function` `findCullen(` `$n` `)` `{` ` ` `return` `(1 << ` `$n` `) * ` `$n` `+ 1;` `}` ` ` `// Driver code` ` ` `$n` `= 2;` ` ` `echo` `findCullen(` `$n` `);` ` ` `// This code is contributed by ajit` `?>` |

## Javascript

`<script>` `// JavaScript program to find Cullen number` `// function to find n'th cullen number` ` ` `function` `findCullen(n)` ` ` `{` ` ` `return` `(1 << n) * n + 1;` ` ` `}` `// Driver Code` ` ` `let n = 2;` ` ` `document.write(findCullen(n));` `</script>` |

**Output:**

9

**Properties of Cullen Numbers:**

- Most of the Cullen Numbers are composite numbers.
- n’th Cullen number is divisible by p = 2n – 1 if p is a prime number of the form 8k – 3.

**Reference: **https://en.wikipedia.org/wiki/Cullen_number

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