28786921 has 4 divisors (see below), whose sum is σ = 28854144. Its totient is φ = 28719700.

The previous prime is 28786913. The next prime is 28786931. The reversal of 28786921 is 12968782.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 28786921 - 2³ = 28786913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28786931) 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 3 ways as a sum of consecutive naturals, for example, 32965 + ... + 33826.

It is an arithmetic number, because the mean of its divisors is an integer number (7213536).

Almost surely, 2^28786921 is an apocalyptic number.

It is an amenable number.

28786921 is a deficient number, since it is larger than the sum of its proper divisors (67223).

28786921 is an equidigital number, since it uses as much as digits as its factorization.

28786921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67222.

The product of its digits is 96768, while the sum is 43.

The square root of 28786921 is about 5365.3444437426. The cubic root of 28786921 is about 306.4773651860.

The spelling of 28786921 in words is "twenty-eight million, seven hundred eighty-six thousand, nine hundred twenty-one".