Demi Lovato -- 7-Figure Deal at 'X Factor'

Demi Lovato is exactly 1/15th the celebrity Britney Spears is ... at least in the salary department.

Sources tell TMZ, the 19-year-old singer's raking in just north of a million to join the gang on "X Factor" -- still damn impressive, but face it ... she's no Britney.

Simon Cowell raved about Demi, praising her accomplishments at such a young age ... insisting she will connect with younger viewers.

As we reported, Britney signed a record $15 million deal to work as a judge on the show -- so Demi's getting table scraps ... but in the TV biz, scraps can make you a millionaire.

And just to show how desperately Demi wanted to appease her new "X Factor" overlords -- we're told the former Disney star even structured her upcoming tour around the "X Factor" tapings.