420 (four hundred ndtwenty) is the

natural number In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and ordering (as in "this is the ''third'' largest city in the country"). Numbers used for counting are called ''Cardinal n ...

following 419 and preceding 421.

In mathematics

420 is: *the sum of four consecutive primes (101 + 103 + 107 + 109). *the sum of the first 20 positive even numbers. *a

zero 0 (zero) is a number representing an empty quantity. In place-value notation such as the Hindu–Arabic numeral system, 0 also serves as a placeholder numerical digit, which works by multiplying digits to the left of 0 by the radix, usual ...

of the

Mertens function In number theory, the Mertens function is defined for all positive integers ''n'' as : M(n) = \sum_^n \mu(k), where \mu(k) is the Möbius function. The function is named in honour of Franz Mertens. This definition can be extended to positive re ...

and is sparsely totient. *a

pronic number A pronic number is a number that is the product of two consecutive integers, that is, a number of the form n(n+1).. The study of these numbers dates back to Aristotle. They are also called oblong numbers, heteromecic numbers,. or rectangular number ...

. *the smallest number divisible by the numbers 1 to 7, and as a consequence of that it is a

Harshad number In mathematics, a harshad number (or Niven number) in a given number base is an integer that is divisible by the sum of its digits when written in that base. Harshad numbers in base are also known as -harshad (or -Niven) numbers. Harshad numbers ...

in every base from 2 to 10 except base 5. *a 141- gonal number. *a balanced number.

In other fields

420 420 may refer to: * 420 (number) * 420 (cannabis culture), informal reference to cannabis use and celebrations on April 20 **California Senate Bill 420 or the Medical Marijuana Program Act *AD 420, a year in the 5th century of the Julian calendar * ...

is a slang term that refers to the consumption of

cannabis ''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: '' Cannabis sativa'', '' C. indica'', and '' C. ruderalis''. Alternative ...

April 20 Events Pre-1600 * 1303 – The Sapienza University of Rome is instituted by a bull of Pope Boniface VIII. 1601–1900 * 1653 – Oliver Cromwell dissolves England's Rump Parliament. * 1657 – English Admiral Robert Blake destroy ...

th is commonly celebrated as a holiday dedicated to the drug, due to the numerical form of the day being 4/20. *

is the country calling code for

Czech Republic The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...

References

{{Integers, 4 Integers Internet memes