6400021 has 4 divisors (see below), whose sum is σ = 6414912. Its totient is φ = 6385132.

The previous prime is 6400019. The next prime is 6400033. The reversal of 6400021 is 1200046.

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 6400021 - 2¹ = 6400019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 6399974 and 6400010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6400091) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6781 + ... + 7666.

It is an arithmetic number, because the mean of its divisors is an integer number (1603728).

Almost surely, 2^6400021 is an apocalyptic number.

It is an amenable number.

6400021 is a deficient number, since it is larger than the sum of its proper divisors (14891).

6400021 is a wasteful number, since it uses less digits than its factorization.

6400021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14890.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 6400021 is about 2529.8262786207. The cubic root of 6400021 is about 185.6637564138.

Adding to 6400021 its reverse (1200046), we get a palindrome (7600067).

The spelling of 6400021 in words is "six million, four hundred thousand, twenty-one".