what about: 10011010111011000010110 ?
Seriously though,
i name them after their tomb world, so mine are just referred to as 'Kathek', or 'of Kathek'.
i got lazy with the necron lord though and blatently ripped off Russel T Davies for the lord's given name by the Eldar: 'The Oncoming Storm', and i also sometimes put the two together to describe the army - 'The Oncoming Storm of Kathek'