420 (number)

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

420 is:

• the sum of four consecutive primes (${\displaystyle 101+103+107+109}$).
• the sum of the first twenty positive even numbers.
• a zero of the Mertens function^[1] and is sparsely totient.^[2]
• a pronic number.^[3]
• The least common multiple of numbers from 1 through 7;^[4] as a consequence of that, it is a Harshad number in bases 2 to 10, except in base 5.
• a 141-gonal number.^{[citation needed]}
• a balanced number.^[5]
• largely composite number^[6]

• 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".^[7]
• 420 is the country calling code for Czech Republic.