20 (twenty) is a positive integer following 19 and preceding 21. Its ordinal form is written "20th" or "twentieth".
20 is an even composite number.
20 is the 4th tetrahedral number.
The number eπ − π is almost equal to 20. The emphasis is on “almost”, since π and eπ are algebraically independent.
In googology Edit
In Greek-based number-naming systems, 20 is associated with prefix "icosa-", and with prefix "viginti-" in Latin systems.
20 is the base of a googologism by Sbiis Saibian called menger sponge. It is equal to 20^3###^^^###3 in Extended Cascading-E Notation.
Wiki user Denis Maksudov calls this number unalum, and it's equal to \(f_1(10)\) using the fast-growing hierarchy.
As a cash denomination Edit
Some currencies, such as the euro 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 Edit
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.
- ↑ Traveling To The Infinity