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.
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.
- ↑ Traveling To The Infinity