That is a very unusual error code, as they are usually just five or six digits long, so where are you seeing this error code appear?
As if you were trying to go online either in a video game multiplayer feature or through the DSi it its DSi Shop and/or updating the system, that is where you will receive the five or six digit error code that when you use the error code lookup, it gives information about why the DSi can not connect to the Internet and possible troubleshooting corrections you can try.
But with this long of an error code, does it occur when you are trying to just play a video game, or even when you are just powering up your DSi, as that type of error code can't be found in the error code lookup feature?
But no matter where this error code appears, you really should give a call to Nintendo's 1-800-255-3700 (6 am ~ 7 pm Pacific, everyday) Customer Service number and they will be able to tell you what it means and help you correct it over the phone if it is some type of Internet connection problem.:)
And if it is something else and is a problem with your DSi, they can figure that out over the phone and set up a repair is that is determined what is needed for this type of error code.