title: How to convert/cast NSNumber to Int64?
body: <p>Just like the title says. I had to store <code>Int64</code> in <code>NSUserDefaults</code> and the only way I found to do that was storing it as <code>NSNumber</code> like</p>
  
  <pre><code>NSNumber(longLong: someInt64)
  </code></pre>
  
  <p>but I don't know how to convert it back to Int64.</p>