Actually, I think the current #1 wallet is just the former #2 wallet unchanged, as it had about 375k coins yesterday... It appears that the former #1, the wallet that was growing rapidly up to 700k NAUT, might be emptied from Bittrex.
Yes I spoke too soon, about 20-30 minutes later the rest was completely emptied so now the 375k is the largest. That's $40k worth of coins!