28189921 has 2 divisors, whose sum is σ = 28189922. Its totient is φ = 28189920.

The previous prime is 28189891. The next prime is 28189963. The reversal of 28189921 is 12998182.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16900321 + 11289600 = 4111^2 + 3360^2 .

It is a cyclic number.

It is not a de Polignac number, because 28189921 - 2⁷ = 28189793 is a prime.

It is not a weakly prime, because it can be changed into another prime (28189981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14094960 + 14094961.

It is an arithmetic number, because the mean of its divisors is an integer number (14094961).

Almost surely, 2^28189921 is an apocalyptic number.

It is an amenable number.

28189921 is a deficient number, since it is larger than the sum of its proper divisors (1).

28189921 is an equidigital number, since it uses as much as digits as its factorization.

28189921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 40.

The square root of 28189921 is about 5309.4181413786. The cubic root of 28189921 is about 304.3439126403.

The spelling of 28189921 in words is "twenty-eight million, one hundred eighty-nine thousand, nine hundred twenty-one".