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

Question

This is a problem from Project Euler, and this question includes some source code, so consider this your spoiler alert, in case you are interested in solving it yourself. It

Answer 1

This is not a serious answer—just an observation.

Although it is a good challenge to try to beat Project Euler using only one programming language, I believe the site aims to further the horizons of all programmers who attempt it. In other words, consider using a different programming language.

A Common Lisp solution to the problem could be as simple as

(defun sum_digits (x)
    (if (= x 0)
        0
        (+ (mod x 10) (sum_digits (truncate (/ x 10))))))

(print (sum_digits (expt 2 1000)))