Fancy number currency notes are banknotes sought after by collectors due to their serial numbers. These serial numbers have specific characteristics that make them desirable. Here are some of the traits that can make a currency note a "fancy number":

• Repeating digits: Serial numbers with sequences of repeating digits, like 777777 or 123456, are popular.
• Low numbers: Notes with serial numbers starting with low numbers, like 000001 or 111111, are considered fancy.
• Matching digits: Notes where the prefix (letters before the number) and the serial number digits have some connection, like "AB 121212" are interesting to collectors.
• Lucky numbers: Numbers considered lucky in certain cultures, like "8" in China, can make a note fancy.