311, 319, 312, 301, 307, 308, 309, 320, 338, 378, 310, 313, 314, 317, 330, 335, 369, 318.
Some of the above numerics have more than one meaning and may not be whois/whowas related on some servers. There's too much coding involved to tell you exactly how mIRC handles each one.
As with most numerics, I add new ones when people report them, since it's impossible to keep track of new numerics across all irc servers, so I'm sure I'm missing a few whois/whowas related numerics.