28756881 has 12 divisors (see below), whose sum is σ = 42660852. Its totient is φ = 18652896.

The previous prime is 28756873. The next prime is 28756909. The reversal of 28756881 is 18865782.

28756881 is a `hidden beast` number, since 2 + 8 + 7 + 568 + 81 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 23040000 + 5716881 = 4800^2 + 2391^2 .

It is not a de Polignac number, because 28756881 - 2³ = 28756873 is a prime.

It is a super-2 number, since 2×28756881² = 1653916409696322, which contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (28756801) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 42846 + ... + 43511.

It is an arithmetic number, because the mean of its divisors is an integer number (3555071).

Almost surely, 2^28756881 is an apocalyptic number.

It is an amenable number.

28756881 is a deficient number, since it is larger than the sum of its proper divisors (13903971).

28756881 is a wasteful number, since it uses less digits than its factorization.

28756881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86400 (or 86397 counting only the distinct ones).

The product of its digits is 215040, while the sum is 45.

The square root of 28756881 is about 5362.5442655516. The cubic root of 28756881 is about 306.3707220296.

The spelling of 28756881 in words is "twenty-eight million, seven hundred fifty-six thousand, eight hundred eighty-one".