420 is the natural number following 419 and preceding 421.

420 is the sum of four consecutive primes (101 + 103 + 107 + 109). 420 is a zero of the Mertens function and is sparsely totient. It is a pronic number, and the smallest number divisible by the numbers 1 to 7, and as a consequence of that it is a Harshad number in every base from 2 to 10 except base 5. It is a 141-gonal number.

420 is also associated with cannabis culture. 420 also refers to a con-artist, trickster in India and Pakistan, see Section 420.

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