6420021 has 4 divisors (see below), whose sum is σ = 8560032. Its totient is φ = 4280012.

The previous prime is 6419989. The next prime is 6420023. The reversal of 6420021 is 1200246.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 6420021 - 2⁵ = 6419989 is a prime.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6420023) 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 3 ways as a sum of consecutive naturals, for example, 1070001 + ... + 1070006.

It is an arithmetic number, because the mean of its divisors is an integer number (2140008).

Almost surely, 2^6420021 is an apocalyptic number.

It is an amenable number.

6420021 is a deficient number, since it is larger than the sum of its proper divisors (2140011).

6420021 is a wasteful number, since it uses less digits than its factorization.

6420021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2140010.

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 6420021 is about 2533.7760358800. The cubic root of 6420021 is about 185.8569544178.

Adding to 6420021 its reverse (1200246), we get a palindrome (7620267).

The spelling of 6420021 in words is "six million, four hundred twenty thousand, twenty-one".