Size of Compiled Program

[Martin Tschierschke via Digitalmars-d-learn]

When I was writing a small speed test - D versus Ruby,
calculating the first n prime numbers, I realized, that for small 
n
Ruby may be faster, than compiling and executing with D.
But for n = 1,000,000 D outperforms Ruby by app. 10x.

Looking at the size of my prime executable, it was around 800 kB 
with DMD
and even with optimization and "gdc -Os" > 1 MB.
Why is such a short program resulting in a so big binary?
-----------------------------------------------------------------------------
import std.stdio;
import std.conv;
int[] prime; // Dynamic Array of Prime

// Ist n durch eine der zahlen in prime teilbar?
bool teilbar(int n){
         for(auto i=0; prime[i]*prime[i]<=n ; i++){
                 if (n%prime[i]==0) return true;
         }
         return false;

}

void main(string[] args)   // first parameter number of primes to 
calculate
{
         auto anzahl = 10; // default
         prime ~= 2;       // first element of the array
         if(args.length==2){
                 anzahl = to!int(args[1]);}
         auto pruefe=1;
         while (prime.length <= anzahl){
                 pruefe+=2;
                 if(!teilbar(pruefe)){
                         write(" ",pruefe);
                         prime ~= pruefe; // append the array
                 }
         }

         write("\n das wars...:",prime.length);
}