Unless there is some mathematical answer you might use (or write your own minimal) large number class. For example I wrote my own small Large class for this and the following user program:

Code:

`int main()`

{

Large num("1");

for (int i = 0; i != 1000; ++i) {

num.multiply_by_two();

}

std::cout << num << '\n' << num.sum_digits() << '\n';

}

And got the result (hope it is correct, seemed to work ok for smaller numbers):

10715086071862673209484250490600018105614048117055 33607443750388370351051124936122493198378815695858 12759467291755314682518714528569231404359845775746 98574803934567774824230985421074605062371141877954 18215304647498358194126739876755916554394607706291 45711964776865421676604298316526243868372056680693 76

1366