> For the complete documentation index, see [llms.txt](https://maksimdan.gitbook.io/interview-practice-problems/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://maksimdan.gitbook.io/interview-practice-problems/project_eular/16_power_digit_sum.md).

# 16 Power Digit Sum

2^15 = 32768 and the sum of its digits is $$3 + 2 + 7 + 6 + 8 = 26.$$

What is the sum of the digits of the number 2^1000

```
#include <iostream>
#include <limits>
#include <vector>
#include <math.h>

using namespace std;

void pause() { cin.ignore(numeric_limits<streamsize>::max(), '\n'); }

// For reference, LLONG_MAX = 9223372036854775807 (2^63-1) or greater and
// ULLONG_MAX = 18446744073709551615 (2^64-1) or greater

int main()
{
    unsigned long long int first = pow(2, 63);
    unsigned long long int second = pow(2, 37);
    cout << first << endl;
    cout << second << endl;
    pause();
}
```

Solution: 1366