Serial number 7777717 is considered "near solid" which occurs when all the digits are the same except one. It helps that the non-matching digit is close to the right side, because then "near solid" takes on a double meaning, i.e., your note was actually physically near the solid-numbered note, 7777777.
There are collectors who seem to like fancy numbers like this, so if the note is in decent shape, it's worth a few more dollars than 1971HemiCuda's assessment. But that's just my opinion, I could be wrong.
