28765681 has 4 divisors (see below), whose sum is σ = 32875072. Its totient is φ = 24656292.

The previous prime is 28765679. The next prime is 28765703. The reversal of 28765681 is 18656782.

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, and also an emirpimes, since its reverse is a distinct semiprime: 18656782 = 2 ⋅9328391.

It is a cyclic number.

It is not a de Polignac number, because 28765681 - 2¹ = 28765679 is a prime.

It is a super-2 number, since 2×28765681² = 1654928806787522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28765621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2054685 + ... + 2054698.

It is an arithmetic number, because the mean of its divisors is an integer number (8218768).

Almost surely, 2^28765681 is an apocalyptic number.

It is an amenable number.

28765681 is a deficient number, since it is larger than the sum of its proper divisors (4109391).

28765681 is an equidigital number, since it uses as much as digits as its factorization.

28765681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4109390.

The product of its digits is 161280, while the sum is 43.

The square root of 28765681 is about 5363.3647088372. The cubic root of 28765681 is about 306.4019700567.

The spelling of 28765681 in words is "twenty-eight million, seven hundred sixty-five thousand, six hundred eighty-one".