20

20 (twenty) is a positive integer following 19 and preceding 21. Its ordinal form is written "20th" or "twentieth".
== Properties ==
*20 is an .
*20 is the 4th .
*20 is the smallest number with abundance 2.
*The number eπ − π is almost equal to 20. The emphasis is on “almost”, since π and eπ are .
== In googology ==
*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 coined the name unalum for this number, and it's equal to \(f_1(10)\) using the fast-growing hierarchy.Traveling To The Infinity
*Nirvana Supermind coined the name zero-binol for this number, and it's equal to Q<10,2> using quick array notation. Numbers from quick array notation - Integral View (accessed/retrieved 2021-06-19)
== As a cash denomination ==
Some currencies, such as the , the and the , have banknotes with this number in the denomination.
Some currencies, such as the and the , have coins with this number in the denomination.
== In pope numbering ==
Its Roman numeral (XX) has never been used in a name of a or an , unlike all the other Roman numerals from I to XXIII. In particular, the papal name has been skipped.
== Sources ==
Category:Numbers
Category:Banknote denominations
Category:Class 1
Category:Coin denominations
Category:Non-powers
Category:Numbers 0-99
Category:Numbers with 1 to 2 digits