Every particular string may be made memorable, but you'd have to memorize it. Instead of it being natural, as in: a natural extension of how people think about things.
Back in the day I worked for BT and had memorable mail addresses such as 018222211 (Prestel) and 80:BTG174 (Dialcom/Telecom Gold) at least the Telecom Gold ones where slightly memorable as the prefix BTG stood for British Telecom Gold.
