user3540: http://arduino.cc/en/Reference/pinMode notes that

The analog input pins can be used as digital pins, referred to as A0, A1, etc.

Is it possible to configure these pins as digital output pins as well?

user3540: Yes.
http://arduino.cc/en/Tutorial/AnalogInputPins states

The analog pins can be used identically to the digital pins, using the aliases A0 (for analog input 0), A1, etc. For example, the code would look like this to set analog pin 0 to an output, and to set it HIGH:

pinMode(A0, OUTPUT);
digitalWrite(A0, HIGH)

There are several caveats on that page regarding this.

3540: <p><a href="http://arduino.cc/en/Reference/pinMode" rel="nofollow">http://arduino.cc/en/Reference/pinMode</a> notes that</p>

<blockquote>
  <p>The analog input pins can be used as digital pins, referred to as A0, A1, etc.</p>
</blockquote>

<p>Is it possible to configure these pins as digital output pins as well?</p>
 3540: <p>Yes.</p>

<p><a href="http://arduino.cc/en/Tutorial/AnalogInputPins" rel="nofollow">http://arduino.cc/en/Tutorial/AnalogInputPins</a> states</p>

<blockquote>
  <p>The analog pins can be used identically to the digital pins, using the aliases A0 (for analog input 0), A1, etc. For example, the code would look like this to set analog pin 0 to an output, and to set it HIGH:</p>
</blockquote>

<pre><code>pinMode(A0, OUTPUT);
digitalWrite(A0, HIGH)
</code></pre>

<p>There are several caveats on that page regarding this.</p>
