28565881 has 4 divisors (see below), whose sum is σ = 28577700. Its totient is φ = 28554064.

The previous prime is 28565869. The next prime is 28565891. The reversal of 28565881 is 18856582.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 17774656 + 10791225 = 4216^2 + 3285^2 .

It is a cyclic number.

It is not a de Polignac number, because 28565881 - 2¹⁹ = 28041593 is a prime.

It is a super-2 number, since 2×28565881² = 1632019114612322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28565891) 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, 826 + ... + 7603.

It is an arithmetic number, because the mean of its divisors is an integer number (7144425).

Almost surely, 2^28565881 is an apocalyptic number.

It is an amenable number.

28565881 is a deficient number, since it is larger than the sum of its proper divisors (11819).

28565881 is an equidigital number, since it uses as much as digits as its factorization.

28565881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11818.

The product of its digits is 153600, while the sum is 43.

The square root of 28565881 is about 5344.7058852663. The cubic root of 28565881 is about 305.6909213456.

It can be divided in two parts, 285 and 65881, that added together give a palindrome (66166).

The spelling of 28565881 in words is "twenty-eight million, five hundred sixty-five thousand, eight hundred eighty-one".