28728931 has 32 divisors (see below), whose sum is σ = 38361600. Its totient is φ = 20839680.

The previous prime is 28728923. The next prime is 28728941. The reversal of 28728931 is 13982782.

It is a 8-Lehmer number, since φ(28728931) divides (28728931-1)⁸.

It is a cyclic number.

It is not a de Polignac number, because 28728931 - 2³ = 28728923 is a prime.

It is a super-2 number, since 2×28728931² = 1650702952805522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28728911) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 106665 + ... + 106933.

It is an arithmetic number, because the mean of its divisors is an integer number (1198800).

Almost surely, 2^28728931 is an apocalyptic number.

28728931 is a deficient number, since it is larger than the sum of its proper divisors (9632669).

28728931 is a wasteful number, since it uses less digits than its factorization.

28728931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 379.

The product of its digits is 48384, while the sum is 40.

The square root of 28728931 is about 5359.9375929203. The cubic root of 28728931 is about 306.2714317363.

The spelling of 28728931 in words is "twenty-eight million, seven hundred twenty-eight thousand, nine hundred thirty-one".