28640931 has 16 divisors (see below), whose sum is σ = 43004928. Its totient is φ = 16797600.

The previous prime is 28640917. The next prime is 28640939. The reversal of 28640931 is 13904682.

It is not a de Polignac number, because 28640931 - 2⁹ = 28640419 is a prime.

It is a super-2 number, since 2×28640931² = 1640605857093522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a junction number, because it is equal to n+sod(n) for n = 28640892 and 28640901.

It is not an unprimeable number, because it can be changed into a prime (28640939) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12976 + ... + 15021.

It is an arithmetic number, because the mean of its divisors is an integer number (2687808).

Almost surely, 2^28640931 is an apocalyptic number.

28640931 is a deficient number, since it is larger than the sum of its proper divisors (14363997).

28640931 is a wasteful number, since it uses less digits than its factorization.

28640931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28042.

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 28640931 is about 5351.7222461559. The cubic root of 28640931 is about 305.9583970951.

The spelling of 28640931 in words is "twenty-eight million, six hundred forty thousand, nine hundred thirty-one".