title: write a recursive function that takes and integer and returns "True' if all of its digits are prime numbers
body: <p>I have to write a Python recursive function that takes an integer as an argument and returns <code>True</code> if all of its digits are prime numbers.
     e.g.</p>
  
  <pre><code>    allPrime(976)
        False
      allPrime(357)
        True
  </code></pre>
  
  <p>This is what I've done so far</p>
  
  <pre><code>def allPrime(n):
      h=str(n)
      for i in range(len(h)):
          if h[i] == isPrime(h):
              return True
          else:
              return False
  </code></pre>