# Twisted Prime Number

A number is said to be twisted prime if it is a prime number and reverse of the number is also a prime number.

Examples:

```Input : 97
Output : Twisted Prime Number
Explanation: 97 is a prime number
and its reverse 79 is also a prime
number.

Input : 43
Output : Not a Twisted Prime Number
Explanation: 43 is a prime number
but its reverse 34 is not a prime
number.
```

## Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

The idea is first check if n is a prime number then reverse the number n and check reversed n is a prime number or not.

We use methods of below two articles.
1) Check if a number is prime (School Method)
2) Reverse digits of a number.

## C/C++

 `// C/C++ program to check if a given number ` `// is Twisted Prime or not ` `#include ` `using` `namespace` `std; ` ` `  `// Returns reverse of n ` `int` `reverse(``int` `n) ` `{ ` `    ``int` `rev = 0, r; ` `    ``while` `(n > 0) { ` `        ``r = n % 10; ` `        ``rev = rev * 10 + r; ` `        ``n /= 10; ` `    ``} ` `    ``return` `rev; ` `} ` ` `  `// Returns true if n is prime ` `bool` `isPrime(``int` `n) ` `{ ` `    ``// Corner cases ` `    ``if` `(n <= 1) ` `        ``return` `false``; ` `    ``if` `(n <= 3) ` `        ``return` `true``; ` ` `  `    ``// This is checked so that we can skip ` `    ``// middle five nbers in below loop ` `    ``if` `(n % 2 == 0 || n % 3 == 0) ` `        ``return` `false``; ` ` `  `    ``for` `(``int` `i = 5; i * i <= n; i = i + 6) ` `        ``if` `(n % i == 0 || n % (i + 2) == 0) ` `            ``return` `false``; ` ` `  `    ``return` `true``; ` `} ` ` `  `// function to check Twisted Prime nber ` `bool` `checkTwistedPrime(``int` `n) ` `{ ` `    ``if` `(isPrime(n) == ``false``) ` `        ``return` `false``; ` ` `  `    ``return` `isPrime(reverse(n)); ` `} ` ` `  `// Driver Code ` `int` `main(``void``) ` `{ ` `    ``// Printing Twisted Prime nbers upto 200 ` `    ``cout << ``"First few Twisted Prime nbers are :- n"``; ` `    ``for` `(``int` `i = 2; i <= 200; i++) ` `        ``if` `(checkTwistedPrime(i)) ` `            ``cout << i << ``" "``; ` ` `  `    ``return` `0; ` `} ` `// This code is contributed by Nikita Tiwari `

## Java

 `// Java program to check if a given number ` `// is Twisted Prime or not ` `import` `java.io.*; ` `import` `java.math.*; ` ` `  `class` `GFG ` `{ ` `    ``static` `int` `reverse(``int` `n) ` `    ``{ ` `        ``int` `rev = ``0``, r; ` `        ``while` `(n > ``0``) ` `        ``{ ` `            ``r = n % ``10``; ` `            ``rev = rev * ``10` `+ r; ` `            ``n /= ``10``; ` `        ``} ` `        ``return` `rev; ` `    ``} ` `    ``static` `boolean` `isPrime(``int` `n) ` `    ``{ ` `        ``// Corner cases ` `        ``if` `(n <= ``1``) ` `            ``return` `false``; ` `        ``if` `(n <= ``3``) ` `            ``return` `true``; ` ` `  `        ``// This is checked so that we can skip ` `        ``// middle five numbers in below loop ` `        ``if` `(n % ``2` `== ``0` `|| n % ``3` `== ``0``) ` `            ``return` `false``; ` ` `  `        ``for` `(``int` `i = ``5``; i * i <= n; i = i + ``6``) ` `            ``if` `(n % i == ``0` `|| n % (i + ``2``) == ``0``) ` `                ``return` `false``; ` ` `  `        ``return` `true``; ` `    ``} ` ` `  `    ``// function to check Twisted Prime Number ` `    ``static` `boolean` `checkTwistedPrime(``int` `n) ` `    ``{ ` `        ``if` `(isPrime(n) == ``false``) ` `            ``return` `false``; ` ` `  `        ``return` `isPrime(reverse(n)); ` `    ``} ` ` `  `    ``// Driver Code ` `    ``public` `static` `void` `main(String args[]) ` `    ``throws` `IOException ` `    ``{ ` `        ``// Printing Twisted Prime Numbers upto 200 ` `        ``System.out.println(``"First few Twisted Prime"` `+ ` `        ``" Numbers are :- n"``); ` `        ``for` `(``int` `i = ``2``; i <= ``200``; i++) ` `            ``if` `(checkTwistedPrime(i)) ` `                ``System.out.print(i + ``" "``); ` `    ``} ` `} ` `// This code is contributed by Nikita Tiwari. `

## Python

 `# Python program to check if a given number ` `# is Twisted Prime or not ` ` `  `def` `reverse(n) : ` `    ``rev ``=` `0` ` `  `    ``# reversing the nber ` `    ``while` `n > ``0` `: ` `        ``r ``=` `n ``%` `10` `        ``rev ``=` `rev ``*` `10` `+` `r ` `        ``n ``=` `n ``/` `10` `    ``return` `rev ` ` `  `# Returns true if n is prime, else false ` `def` `isPrime(n) : ` ` `  `    ``# Corner cases ` `    ``if` `(n <``=` `1``): ` `        ``return` `False` `    ``if` `(n <``=` `3``): ` `        ``return` `True` ` `  `    ``# This is checked so that we can skip ` `    ``# middle five nbers in below loop ` `    ``if` `(n ``%` `2` `=``=` `0` `or` `n ``%` `3` `=``=` `0``): ` `        ``return` `False` ` `  `    ``i ``=` `5` `    ``while` `(i ``*` `i <``=` `n): ` `        ``if` `(n ``%` `i ``=``=` `0` `or` `n ``%` `(i ``+` `2``) ``=``=` `0``): ` `            ``return` `False` `        ``i ``=` `i ``+` `6` ` `  `    ``return` `True``; ` ` `  `# function to check Twisted Prime nber ` `def` `checkTwistedPrime (n) : ` `    ``if` `(isPrime(n) ``=``=` `False``): ` `        ``return` `False` ` `  `    ``return` `isPrime(reverse(n)) ` ` `  `# Driver Code ` `# Printing Twisted Prime nbers upto 200 ` `print` `"First few Twisted Prime numbers are :- "` `i ``=` `2` `while` `i<``=` `200` `: ` `    ``if` `(checkTwistedPrime(i) ``=``=` `True``) : ` `        ``print` `i, ` `    ``i ``=` `i ``+` `1` ` `  ` `  `# This code is contributed by Nikita Tiwari. `

## C#

 `// C# program to check if a given  ` `// number is Twisted Prime or not ` `using` `System; ` ` `  `class` `GFG ` `{ ` `static` `int` `reverse(``int` `n) ` `{ ` `    ``int` `rev = 0, r; ` `    ``while` `(n > 0) ` `    ``{ ` `        ``r = n % 10; ` `        ``rev = rev * 10 + r; ` `        ``n /= 10; ` `    ``} ` `    ``return` `rev; ` `} ` ` `  `static` `bool` `isPrime(``int` `n) ` `{ ` `    ``// Corner cases ` `    ``if` `(n <= 1) ` `        ``return` `false``; ` `    ``if` `(n <= 3) ` `        ``return` `true``; ` ` `  `    ``// This is checked so that  ` `    ``// we can skip middle five ` `    ``// numbers in below loop ` `    ``if` `(n % 2 == 0 || n % 3 == 0) ` `        ``return` `false``; ` ` `  `    ``for` `(``int` `i = 5;  ` `             ``i * i <= n; i = i + 6) ` `        ``if` `(n % i == 0 ||  ` `            ``n % (i + 2) == 0) ` `            ``return` `false``; ` ` `  `    ``return` `true``; ` `} ` ` `  `// function to check  ` `// Twisted Prime Number ` `static` `bool` `checkTwistedPrime(``int` `n) ` `{ ` `    ``if` `(isPrime(n) == ``false``) ` `        ``return` `false``; ` ` `  `    ``return` `isPrime(reverse(n)); ` `} ` ` `  `// Driver Code ` `static` `public` `void` `Main () ` `{ ` `     `  `// Printing Twisted Prime ` `// Numbers upto 200 ` `Console.WriteLine(``"First few Twisted Prime"` `+ ` `                         ``" Numbers are :- "``); ` `                          `  `for` `(``int` `i = 2; i <= 200; i++) ` `    ``if` `(checkTwistedPrime(i)) ` `        ``Console.Write(i + ``" "``); ` `} ` `} ` ` `  `// This code is contributed by ajit `

## PHP

 ` 0){ ` `        ``\$r` `= ``\$n` `% 10; ` `        ``\$rev` `= ``\$rev` `* 10 + ``\$r``; ` `        ``\$n` `= (int)(``\$n` `/ 10); ` `        ``} ` `    ``return` `\$rev``; ` `} ` ` `  `// Returns true if n is prime, else false ` `function` `isPrime(``\$n``) ` `{ ` `    ``// Corner cases ` `    ``if` `(``\$n` `<= 1) ` `        ``return` `false; ` `    ``if` `(``\$n` `<= 3) ` `        ``return` `true; ` ` `  `    ``// This is checked so that we can skip ` `    ``// middle five nbers in below loop ` `    ``if` `(``\$n` `% 2 == 0 ``or` `\$n` `% 3 == 0) ` `        ``return` `false; ` ` `  `    ``\$i` `= 5; ` `    ``while` `(``\$i` `* ``\$i` `<= ``\$n``){ ` `        ``if` `(``\$n` `% ``\$i` `== 0 ``or` `\$n` `% (``\$i` `+ 2) == 0) ` `            ``return` `false; ` `        ``\$i` `= ``\$i` `+ 6; ` `        ``} ` ` `  `    ``return` `true; ` `} ` ` `  `// function to check Twisted Prime nber ` `function` `checkTwistedPrime (``\$n``) ` `{ ` `    ``if` `(isPrime(``\$n``) == false) ` `        ``return` `false; ` ` `  `    ``return` `isPrime(reverse(``\$n``)); ` `} ` ` `  `// Driver Code ` `// Printing Twisted Prime nbers upto 200 ` `print``(``"First few Twisted Prime numbers are :- \n"``); ` `\$i` `= 2; ` `while``(``\$i``<= 200) ` `{ ` `    ``if` `(checkTwistedPrime(``\$i``) == true) ` `        ``print``(``\$i``.``" "``); ` `    ``\$i` `= ``\$i` `+ 1; ` `} ` ` `  ` `  `// This code is contributed by mits ` `?> `

Output:

```First few Twisted Prime Numbers are :-
2 3 5 7 11 13 17 31 37 71 73 79 97 101 107 113 131 149 151 157 167 179 181 191 199
```

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Improved By : jit_t, Mithun Kumar

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