When the 3DS launched earlier this year, it did so with disappointing numbers; however, lately, it has been performing incredibly well and has even managed to put up some record numbers over the holiday season.
Famitsu and Enterbrain are reporting that the 3DS has shipped 510,629 units over the past week, bringing its total sales above to 4,135,739 units.
The 510,629 units of 3DSs that were sold broke its previous weekly record of 367,691 units.
The release of Mario Kart 7 and Super Mario 3D Land certainly helped. Both games have surpassed the million units sold mark in domestic sales, which makes them the first 3DS games to reach this achievement. Super Mario 3D Land has sold 1,042,511 units since November 3rd and Mario Kart is has sold 1,082,391 units since December 1st.
[Source]