6406644821 has 4 divisors (see below), whose sum is σ = 6406855392. Its totient is φ = 6406434252.

The previous prime is 6406644787. The next prime is 6406644833. The reversal of 6406644821 is 1284466046.

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 6406644821 - 2²² = 6402450517 is a prime.

It is a super-2 number, since 2×6406644821² = 82090195724892244082, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6406644841) 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, 49955 + ... + 123728.

It is an arithmetic number, because the mean of its divisors is an integer number (1601713848).

Almost surely, 2^6406644821 is an apocalyptic number.

It is an amenable number.

6406644821 is a deficient number, since it is larger than the sum of its proper divisors (210571).

6406644821 is a wasteful number, since it uses less digits than its factorization.

6406644821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210570.

The product of its (nonzero) digits is 221184, while the sum is 41.

The square root of 6406644821 is about 80041.5193571436. The cubic root of 6406644821 is about 1857.2778638407.

The spelling of 6406644821 in words is "six billion, four hundred six million, six hundred forty-four thousand, eight hundred twenty-one".