28057865821 has 4 divisors (see below), whose sum is σ = 28111514272. Its totient is φ = 28004217372.

The previous prime is 28057865813. The next prime is 28057865833. The reversal of 28057865821 is 12856875082.

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 28057865821 - 2³ = 28057865813 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 (28057865021) 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, 26823441 + ... + 26824486.

It is an arithmetic number, because the mean of its divisors is an integer number (7027878568).

Almost surely, 2^28057865821 is an apocalyptic number.

It is an amenable number.

28057865821 is a deficient number, since it is larger than the sum of its proper divisors (53648451).

28057865821 is an equidigital number, since it uses as much as digits as its factorization.

28057865821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53648450.

The product of its (nonzero) digits is 2150400, while the sum is 52.

The spelling of 28057865821 in words is "twenty-eight billion, fifty-seven million, eight hundred sixty-five thousand, eight hundred twenty-one".