Without knowing information such as the series (date) and condition, the best guess is that it's worth $2.
It is not worth anything
Nothing.
$1.00
Assuming the 666 is part of the eight-digit serial number, it's worth one dollar.
twenty dollars
$20.00
10 dollars
Nothing as of yet!
A 20-dollar bill with one serial number is still worth 20 dollars, as the value of the bill is determined by its denomination rather than the number of serial numbers it has. Each U.S. currency note has a unique serial number, but this does not affect its face value. Therefore, regardless of the serial number, the bill retains its worth of 20 dollars.
Nothing you idiot! If it doesn't have a serial stamp on it, it's gay and worth crap!
It's worth $50.
It's still worth $2 in Canada.