title: Django Models Number Field
body: <p>In Django I'm trying to create a model which will contain a field for player's shirt numbers and was wondering if there is a way to restrict the field to be only numerical inputs. Currently I have in the models.py</p>
  
  <pre><code>number = models.CharField(max_length=2)
  </code></pre>
  
  <p>Is there a different field to CharField that will allow me to restrict the input to only numbers?</p>