28565816681 has 4 divisors (see below), whose sum is σ = 28584331392. Its totient is φ = 28547301972.

The previous prime is 28565816647. The next prime is 28565816687. The reversal of 28565816681 is 18661856582.

It is a happy number.

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 28565816681 - 2¹⁰ = 28565815657 is a prime.

It is a super-2 number, since 2×28565816681² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28565816687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9255041 + ... + 9258126.

It is an arithmetic number, because the mean of its divisors is an integer number (7146082848).

Almost surely, 2^28565816681 is an apocalyptic number.

It is an amenable number.

28565816681 is a deficient number, since it is larger than the sum of its proper divisors (18514711).

28565816681 is a wasteful number, since it uses less digits than its factorization.

28565816681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18514710.

The product of its digits is 5529600, while the sum is 56.

The spelling of 28565816681 in words is "twenty-eight billion, five hundred sixty-five million, eight hundred sixteen thousand, six hundred eighty-one".