Most people know the saying, “A dollar saved is a dollar earned.” But did you know some $1 bills are actually worth hundreds—or even thousands—of dollars? While coins often get attention from collectors, paper currency with unusual serial numbers can be just as valuable.

Every U.S. dollar bill carries an eight-digit serial number. Most are ordinary, but rare patterns stand out to collectors. Because the Bureau of Engraving & Printing sometimes removes unusual sequences, those that slip through become highly prized.

One of the most sought-after patterns is the ladder, where numbers run in perfect order, such as 01234567. Radar notes are also popular, with numbers that read the same backward and forward, like 22211222.

Even rarer are super radars, where the middle six digits match, such as 23333332. Collectors also chase repeaters, where a sequence repeats (01570157), or super repeaters, which use only two digits in alternating order, like….