6420821 has 8 divisors (see below), whose sum is σ = 7042464. Its totient is φ = 5805520.

The previous prime is 6420809. The next prime is 6420823. The reversal of 6420821 is 1280246.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 6420821 - 2¹⁰ = 6419797 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6420823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 686 + ... + 3648.

It is an arithmetic number, because the mean of its divisors is an integer number (880308).

Almost surely, 2^6420821 is an apocalyptic number.

It is an amenable number.

6420821 is a deficient number, since it is larger than the sum of its proper divisors (621643).

6420821 is a wasteful number, since it uses less digits than its factorization.

6420821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3171.

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 6420821 is about 2533.9338981118. The cubic root of 6420821 is about 185.8646739869.

The spelling of 6420821 in words is "six million, four hundred twenty thousand, eight hundred twenty-one".