28877981 has 12 divisors (see below), whose sum is σ = 32521692. Its totient is φ = 25608000.

The previous prime is 28877977. The next prime is 28877993. The reversal of 28877981 is 18977882.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 12313081 + 16564900 = 3509^2 + 4070^2 .

It is not a de Polignac number, because 28877981 - 2² = 28877977 is a prime.

It is a super-2 number, since 2×28877981² = 1667875573272722, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28877911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2051 + ... + 7871.

It is an arithmetic number, because the mean of its divisors is an integer number (2710141).

Almost surely, 2^28877981 is an apocalyptic number.

It is an amenable number.

28877981 is a deficient number, since it is larger than the sum of its proper divisors (3643711).

28877981 is a wasteful number, since it uses less digits than its factorization.

28877981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5884 (or 5873 counting only the distinct ones).

The product of its digits is 451584, while the sum is 50.

The square root of 28877981 is about 5373.8236852357. The cubic root of 28877981 is about 306.8001790785.

Subtracting from 28877981 its reverse (18977882), we obtain a palindrome (9900099).

The spelling of 28877981 in words is "twenty-eight million, eight hundred seventy-seven thousand, nine hundred eighty-one".