title: Convert number to and from alphanumeric code
body: <p>Is it possible to convert from numeric to an alphanumeric code like this:</p>
  
  <pre><code>a
  b
  c
  d
  ..
  z
  1
  2
  3
  4
  ..
  aa
  ab
  ac
  ad
  ..
  az
  a1
  a2
  a3
  a4
  ..
  aaa
  aab
  aac
  aad
  ..
  aaz
  aa1
  aa2
  </code></pre>
  
  <p>etc.</p>
  
  <p>I'm trying to convert large numbers to smaller length alphanumeric strings.</p>