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

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

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```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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:

 `// 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); ``    ``} ``} `

Output:

```Yes
No```