Convert a number to the shortest possible character string while retaining uniqueness
<p>I have a number, say "123456", and I need to map it to a string, any string. The only constraint on the map functions are:</p>

<ul>
<li>each number must map to a unique character string (this means the string can be arbitrarily long)</li>
<li>character string can only contain 0-9, a-z, A-Z</li>
</ul>

<p>What map function would produce the shortest strings?</p>

<p>Solutions in JavaScript are preferred.</p>

<p>Note: Clearly the simplest solution is to use the original number, so make sure you solution does better than that. </p>
