function encode(num) {
	  var encoded = '';
	
	  do {
	    encoded = alphabet[num % length] + encoded;
	    num = Math.floor(num / length);
	  } while (num > 0);
	
	  return encoded;
	}
Return a string representing the specified number.

@param {Number} num The number to convert.
@returns {String} The string representation of the number.
@api public