864542821 has 4 divisors (see below), whose sum is σ = 884648512. Its totient is φ = 844437132.

The previous prime is 864542771. The next prime is 864542839. The reversal of 864542821 is 128245468.

It is a happy number.

864542821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 864542821 - 2⁹ = 864542309 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (864542891) 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, 10052781 + ... + 10052866.

It is an arithmetic number, because the mean of its divisors is an integer number (221162128).

Almost surely, 2^864542821 is an apocalyptic number.

It is an amenable number.

864542821 is a deficient number, since it is larger than the sum of its proper divisors (20105691).

864542821 is a wasteful number, since it uses less digits than its factorization.

864542821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20105690.

The product of its digits is 122880, while the sum is 40.

The square root of 864542821 is about 29403.1090362907. The cubic root of 864542821 is about 952.6400511430.

The spelling of 864542821 in words is "eight hundred sixty-four million, five hundred forty-two thousand, eight hundred twenty-one".