# Check if the first and last digit of number N is prime and their sum is less than K

• Last Updated : 27 Apr, 2021

Given a number N, the task is to check if its first and last digit is a prime number and their sum is less than K, or not. If it is, then print Yes, else print No.
Examples:

```Input: N = 322223, K = 10
Output: Yes

Input: N = 62531561, K = 15
Output: No```

Approach:

• Check if the first and last digit of N is prime or not.
• If they are prime, then check if they are less than K or not
• If they are less than K as well, print Yes.
• In any other case, print No.

Below is the implementation of the above approach:

## C++

 `// C++ program to check``// if the first and last digit of number N``// is prime and their sum is less than K``#include ``using` `namespace` `std;` `// Get the First digit of the number``int` `first(``int` `n)``{``    ``int` `a = n;``    ``int` `c = 1;``    ``while` `(a != 0)``    ``{``        ``a /= 10;``        ``c = c * 10;``    ``}``    ``c = c / 10;``    ``int` `fi = n / c;``    ``return` `fi;``}` `// Check if the digit is prime or not``bool` `prime(``int` `n)``{``    ``switch` `(n)``    ``{``        ``case` `2:``            ``return` `true``;``    ` `        ``case` `3:``            ``return` `true``;``    ` `        ``case` `5:``            ``return` `true``;``    ` `        ``case` `7:``            ``return` `true``;``    ` `        ``default``:``            ``return` `false``;``    ``}``}` `// Function to Check if the first``// and last digit of number N is prime``// and their sum is less than K``void` `check(``int` `n, ``int` `k)``{` `    ``// Last digit of the number``    ``int` `l = n % 10;` `    ``// First digit of number``    ``int` `f = first(n);` `    ``// Check if these are prime``    ``bool` `lp = prime(l);``    ``bool` `fp = prime(f);` `    ``// If they are prime``    ``if` `(lp && fp)``    ``{` `        ``// Check if they are less than k or not``        ``if` `(l + f < k)``            ``cout << ``"Yes\n"``;``        ``else``            ``cout << ``"No\n"``;``    ``}``    ``else``    ``{``        ``cout << ``"No\n"``;``    ``}``}` `// Driver code``int` `main()``{``    ``// Test case 1``    ``int` `n = 322223;``    ``int` `k = 10;``    ` `    ``check(n, k);``    ` `    ``// Test case 2``    ``n = 62531561;``    ``k = 15;``    ` `    ``check(n, k);``    ` `    ``return` `0;``}` `// This code is contributed by PrinciRaj1992`

## Java

 `// Java program to check``// if the first and last digit of number N``// is prime and their sum is less than K` `import` `java.lang.*;` `public` `class` `crazy_number {` `    ``// Get the First digit of the number``    ``public` `static` `int` `first(``int` `n)``    ``{``        ``int` `a = n;``        ``int` `c = ``1``;``        ``while` `(a != ``0``) {``            ``a /= ``10``;``            ``c = c * ``10``;``        ``}``        ``c = c / ``10``;``        ``int` `fi = n / c;``        ``return` `fi;``    ``}` `    ``// Check if the digit is prime or not``    ``public` `static` `boolean` `prime(``int` `n)``    ``{` `        ``switch` `(n) {``        ``case` `2``:``            ``return` `true``;` `        ``case` `3``:``            ``return` `true``;` `        ``case` `5``:``            ``return` `true``;` `        ``case` `7``:``            ``return` `true``;` `        ``default``:``            ``return` `false``;``        ``}``    ``}` `    ``// Function to Check if the first``    ``// and last digit of number N is prime``    ``// and their sum is less than K``    ``public` `static` `void` `check(``int` `n, ``int` `k)``    ``{` `        ``// Last digit of the number``        ``int` `l = n % ``10``;` `        ``// First digit of number``        ``int` `f = first(n);` `        ``// Check if these are prime``        ``boolean` `lp = prime(l);``        ``boolean` `fp = prime(f);` `        ``// If they are prime``        ``if` `(lp && fp) {` `            ``// Check if they are less than k or not``            ``if` `(l + f < k)``                ``System.out.println(``"Yes"``);``            ``else``                ``System.out.println(``"No"``);``        ``}``        ``else` `{``            ``System.out.println(``"No"``);``        ``}``    ``}` `    ``// Driver code``    ``public` `static` `void` `main(String args[])``    ``{` `        ``// Test case 1``        ``int` `n = ``322223``;``        ``int` `k = ``10``;` `        ``check(n, k);` `        ``// Test case 2``        ``n = ``62531561``;``        ``k = ``15``;` `        ``check(n, k);``    ``}``}`

## Python3

 `# Python3 program to check if``# the first and last digit of number N``# is prime and their sum is less than K` `# Get the First digit of the number``def` `first(n):``    ``a ``=` `n``    ``c ``=` `1``    ``while` `(a !``=` `0``):``        ``a ``/``/``=` `10``        ``c ``=` `c ``*` `10` `    ``c ``=` `c ``/``/` `10``    ``fi ``=` `n ``/``/` `c``    ``return` `fi` `# Check if the digit is prime or not``def` `prime(n):``    ``if` `n ``in` `[``2``, ``3``, ``5``, ``7``]:``        ``return` `True``    ``else``:``        ``return` `False` `# Function to Check if the first``# and last digit of number N is prime``# and their sum is less than K``def` `check(n, k):` `    ``# Last digit of the number``    ``l ``=` `n ``%` `10` `    ``# First digit of number``    ``f ``=` `first(n)` `    ``# Check if these are prime``    ``lp ``=` `prime(l)``    ``fp ``=` `prime(f)` `    ``# If they are prime``    ``if` `(lp ``and` `fp):` `        ``# Check if they are less than k or not``        ``if` `(l ``+` `f < k):``            ``print``(``"Yes"``)``        ``else``:``            ``print``(``"No"``)``    ``else``:``        ``print``(``"No"``)` `# Driver code` `# Test case 1``n ``=` `322223``k ``=` `10` `check(n, k)` `# Test case 2``n ``=` `62531561``k ``=` `15` `check(n, k)` `# This code is contributed by Mohit kumar`

## C#

 `// C# program to check``// if the first and last digit of number N``// is prime and their sum is less than K``using` `System;` `class` `GFG``{` `    ``// Get the First digit of the number``    ``public` `static` `int` `first(``int` `n)``    ``{``        ``int` `a = n;``        ``int` `c = 1;``        ``while` `(a != 0)``        ``{``            ``a /= 10;``            ``c = c * 10;``        ``}``        ``c = c / 10;``        ``int` `fi = n / c;``        ``return` `fi;``    ``}` `    ``// Check if the digit is prime or not``    ``public` `static` `Boolean prime(``int` `n)``    ``{``        ``switch` `(n)``        ``{``            ``case` `2:``                ``return` `true``;``    ` `            ``case` `3:``                ``return` `true``;``    ` `            ``case` `5:``                ``return` `true``;``    ` `            ``case` `7:``                ``return` `true``;``    ` `            ``default``:``                ``return` `false``;``        ``}``    ``}` `    ``// Function to Check if the first``    ``// and last digit of number N is prime``    ``// and their sum is less than K``    ``public` `static` `void` `check(``int` `n, ``int` `k)``    ``{` `        ``// Last digit of the number``        ``int` `l = n % 10;` `        ``// First digit of number``        ``int` `f = first(n);` `        ``// Check if these are prime``        ``Boolean lp = prime(l);``        ``Boolean fp = prime(f);` `        ``// If they are prime``        ``if` `(lp && fp)``        ``{` `            ``// Check if they are less than k or not``            ``if` `(l + f < k)``                ``Console.WriteLine(``"Yes"``);``            ``else``                ``Console.WriteLine(``"No"``);``        ``}``        ` `        ``else``        ``{``            ``Console.WriteLine(``"No"``);``        ``}``    ``}` `    ``// Driver code``    ``public` `static` `void` `Main(String []args)``    ``{` `        ``// Test case 1``        ``int` `n = 322223;``        ``int` `k = 10;` `        ``check(n, k);` `        ``// Test case 2``        ``n = 62531561;``        ``k = 15;` `        ``check(n, k);``    ``}``}` `// This code is contributed by PrinciRaj1992`

## Javascript

 ``

Output:

```Yes
No```

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