20 (twenty) is a positive integer following 19 and preceding 21. Its ordinal form is written "20th" or "twentieth".
As a cash denomination
Some currencies, such as the euro, the Israeli new shekel and the United States dollar, have banknotes with this number in the denomination.
Some currencies, such as the Czech koruna and the Hungarian forint, have coins with this number in the denomination.
In pope numbering
Its Roman numeral (XX) has never been used in a name of a pope or an antipope, unlike all the other Roman numerals from I to XXIII. In particular, the papal name John XX has been skipped.