My banknotes with the highest coolness factor in relation to the serial number would be my CU $50's with the serial numbers 78888888 and 78888887.
The message from Cool Numbers reads ''Congratulations! You have found an extremely cool number! It has a Universal Coolness Index of 99.51% in relation to the seven in a row, and the super radar gets only 99.47%''.
The website goes on to say ''78888888 contains a 7-of-a-kind together. Only 0.00018% of 8-digit numbers have this combination''. It unfortunately doesn't say how likely the note is to be found crisp out of the bank strap. That might boost the rating up a notch or two. Here is the video I made:
All right, my apologies. You were looking for "almost but not quite" notes, and I completely missed the website that ranks coolness. How about this "almost a ladder":
Quote: This is a very cool number! It has a Universal Coolness Index of 98.3%. 09876500 contains a backwards run of 5. In 0.023% of 8-digit numbers, there are backwards runs of 5 or longer.
Or this "not quite a low serial number star":
Quote: This is a very cool number! It has a Universal Coolness Index of 97.0%. 00001373's digits sum to 14. In 0.32% of 8-digit numbers, the digits sum to at most 14. 00001373 contains a 4-of-a-kind together. Only 0.46% of 8-digit numbers have this combination. 00001373 contains a 4-of-a-kind and 1 pair. Only 2.6% of 8-digit numbers have this combination. 00001373 is a prime number! Only 5.8% of 8-digit numbers are prime. 00001373 has 4 unique digits. In 9.3% of 8-digit numbers, there are 4 or fewer unique digits.
[Sadly, it won't let me enter the star to see if that adds to the coolness or not.]