title: A positive number from 1 to 2^31 -1 in regex
body: <p>I got the following regex that almost does the work but does not exclude zero ...How to do that?</p>
  
  <pre><code>^(\d|\d{1,9}|1\d{1,9}|20\d{8}|213\d{7}|2146\d{6}|21473\d{5}|214747\d{4}|2147482\d{3}|21474835\d{2}|214748364[0-7])$
  </code></pre>
  
  <p>Also can anybody explain a bit how this works?</p>