420 (number) explained

420 (four hundred [and] twenty) is the natural number following 419 and preceding 421.

In mathematics

420 is:

• the sum of four consecutive primes (

).

• the sum of the first twenty positive even numbers.
• a zero of the Mertens function and is sparsely totient.
• a pronic number.
• The least common multiple of numbers from 1 through 7;^[1] as a consequence of that, it is a Harshad number in bases 2 to 10, except in base 5.
• a 141-gonal number.
• a balanced number.
• largely composite number

In other fields

• 420 is a slang term that refers to the consumption of cannabis. April 20th is commonly celebrated as a holiday dedicated to the drug, due the day being notated as 4/20 in the month-day-year format. Because of these associations, 420 has been humorously referred to as the "weed number".^[2]
• 420 is the country calling code for Czech Republic.

Notes and References

1. Web site: A003418 - OEIS . 2024-11-20 . oeis.org.
2. Web site: Associated Press . 2017-04-20 . How marijuana’s high holiday came to be . 2024-11-20 . en-US.