# Find all the prime numbers of given number of digits

Given an integer D, the task is to find all the prime numbers having D digits.

Examples:
Input: D = 1
Output: 2 3 5 7

Input: D = 2
Output: 11 13 17 19 23 29 31 37 41 43 47 53 61 67 71 73 79 83 89 97

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

Approach: Numbers with D digits lie in the range [10(D – 1), 10D – 1]. So, check all the numbers in this interval and to check the number is prime or not, use Sieve of Eratosthenes to generate all the primes.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `const` `int` `sz = 1e5; ` `bool` `isPrime[sz + 1]; ` ` `  `// Function for Sieve of Eratosthenes ` `void` `sieve() ` `{ ` `    ``memset``(isPrime, ``true``, ``sizeof``(isPrime)); ` ` `  `    ``isPrime = isPrime = ``false``; ` ` `  `    ``for` `(``int` `i = 2; i * i <= sz; i++) { ` `        ``if` `(isPrime[i]) { ` `            ``for` `(``int` `j = i * i; j < sz; j += i) { ` `                ``isPrime[j] = ``false``; ` `            ``} ` `        ``} ` `    ``} ` `} ` ` `  `// Function to print all the prime ` `// numbers with d digits ` `void` `findPrimesD(``int` `d) ` `{ ` ` `  `    ``// Range to check integers ` `    ``int` `left = ``pow``(10, d - 1); ` `    ``int` `right = ``pow``(10, d) - 1; ` ` `  `    ``// For every integer in the range ` `    ``for` `(``int` `i = left; i <= right; i++) { ` ` `  `        ``// If the current integer is prime ` `        ``if` `(isPrime[i]) { ` `            ``cout << i << ``" "``; ` `        ``} ` `    ``} ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` ` `  `    ``// Generate primes ` `    ``sieve(); ` `    ``int` `d = 1; ` `    ``findPrimesD(d); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the approach ` `import` `java.util.*; ` ` `  `class` `GFG ` `{ ` `static` `int` `sz = ``100000``; ` `static` `boolean` `isPrime[] = ``new` `boolean``[sz + ``1``]; ` ` `  `// Function for Sieve of Eratosthenes ` `static` `void` `sieve() ` `{ ` `    ``for``(``int` `i = ``0``; i <= sz; i++) ` `    ``isPrime[i] = ``true``; ` `     `  `    ``isPrime[``0``] = isPrime[``1``] = ``false``; ` ` `  `    ``for` `(``int` `i = ``2``; i * i <= sz; i++)  ` `    ``{ ` `        ``if` `(isPrime[i])  ` `        ``{ ` `            ``for` `(``int` `j = i * i; j < sz; j += i)  ` `            ``{ ` `                ``isPrime[j] = ``false``; ` `            ``} ` `        ``} ` `    ``} ` `} ` ` `  `// Function to print all the prime ` `// numbers with d digits ` `static` `void` `findPrimesD(``int` `d) ` `{ ` ` `  `    ``// Range to check integers ` `    ``int` `left = (``int``)Math.pow(``10``, d - ``1``); ` `    ``int` `right = (``int``)Math.pow(``10``, d) - ``1``; ` ` `  `    ``// For every integer in the range ` `    ``for` `(``int` `i = left; i <= right; i++) ` `    ``{ ` ` `  `        ``// If the current integer is prime ` `        ``if` `(isPrime[i])  ` `        ``{ ` `            ``System.out.print(i + ``" "``); ` `        ``} ` `    ``} ` `} ` ` `  `// Driver code ` `public` `static` `void` `main(String args[]) ` `{ ` ` `  `    ``// Generate primes ` `    ``sieve(); ` `    ``int` `d = ``1``; ` `    ``findPrimesD(d); ` `} ` `} ` ` `  `// This code is contributed by Arnab Kundu `

## Python 3

 `# Python 3 implementation of the approach ` `from` `math ``import` `sqrt, ``pow` `sz ``=` `100005` `isPrime ``=` `[``True` `for` `i ``in` `range``(sz ``+` `1``)] ` ` `  `# Function for Sieve of Eratosthenes ` `def` `sieve(): ` `    ``isPrime[``0``] ``=` `isPrime[``1``] ``=` `False` ` `  `    ``for` `i ``in` `range``(``2``, ``int``(sqrt(sz)) ``+` `1``, ``1``): ` `        ``if` `(isPrime[i]): ` `            ``for` `j ``in` `range``(i ``*` `i, sz, i): ` `                ``isPrime[j] ``=` `False` ` `  `# Function to print all the prime ` `# numbers with d digits ` `def` `findPrimesD(d): ` `     `  `    ``# Range to check integers ` `    ``left ``=` `int``(``pow``(``10``, d ``-` `1``)) ` `    ``right ``=` `int``(``pow``(``10``, d) ``-` `1``) ` ` `  `    ``# For every integer in the range ` `    ``for` `i ``in` `range``(left, right ``+` `1``, ``1``): ` `         `  `        ``# If the current integer is prime ` `        ``if` `(isPrime[i]): ` `            ``print``(i, end ``=` `" "``) ` `         `  `# Driver code ` `if` `__name__ ``=``=` `'__main__'``: ` `     `  `    ``# Generate primes ` `    ``sieve() ` `    ``d ``=` `1` `    ``findPrimesD(d) ` `     `  `# This code is contributed by Surendra_Gangwar `

## C#

 `// C# implementation of the approach ` `using` `System; ` ` `  `class` `GFG ` `{ ` `     `  `static` `int` `sz = 100000; ` `static` `bool` `[]isPrime = ``new` `bool``[sz + 1]; ` ` `  `// Function for Sieve of Eratosthenes ` `static` `void` `sieve() ` `{ ` `    ``for``(``int` `i = 0; i <= sz; i++) ` `    ``isPrime[i] = ``true``; ` `     `  `    ``isPrime = isPrime = ``false``; ` ` `  `    ``for` `(``int` `i = 2; i * i <= sz; i++)  ` `    ``{ ` `        ``if` `(isPrime[i])  ` `        ``{ ` `            ``for` `(``int` `j = i * i; j < sz; j += i)  ` `            ``{ ` `                ``isPrime[j] = ``false``; ` `            ``} ` `        ``} ` `    ``} ` `} ` ` `  `// Function to print all the prime ` `// numbers with d digits ` `static` `void` `findPrimesD(``int` `d) ` `{ ` ` `  `    ``// Range to check integers ` `    ``int` `left = (``int``)Math.Pow(10, d - 1); ` `    ``int` `right = (``int``)Math.Pow(10, d) - 1; ` ` `  `    ``// For every integer in the range ` `    ``for` `(``int` `i = left; i <= right; i++) ` `    ``{ ` ` `  `        ``// If the current integer is prime ` `        ``if` `(isPrime[i])  ` `        ``{ ` `            ``Console.Write(i + ``" "``); ` `        ``} ` `    ``} ` `} ` ` `  `// Driver code ` `static` `public` `void` `Main () ` `{ ` `     `  `    ``// Generate primes ` `    ``sieve(); ` `    ``int` `d = 1; ` `    ``findPrimesD(d); ` ` `  `} ` `} ` ` `  `// This code is contributed by ajit. `

Output:

```2 3 5 7
```

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.

My Personal Notes arrow_drop_up Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.