28055921 has 4 divisors (see below), whose sum is σ = 28585332. Its totient is φ = 27526512.

The previous prime is 28055903. The next prime is 28055939. The reversal of 28055921 is 12955082.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (28055903) and next prime (28055939).

It can be written as a sum of positive squares in 2 ways, for example, as 16900321 + 11155600 = 4111^2 + 3340^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28055921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28055021) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 264626 + ... + 264731.

It is an arithmetic number, because the mean of its divisors is an integer number (7146333).

Almost surely, 2^28055921 is an apocalyptic number.

It is an amenable number.

28055921 is a deficient number, since it is larger than the sum of its proper divisors (529411).

28055921 is an equidigital number, since it uses as much as digits as its factorization.

28055921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 529410.

The product of its (nonzero) digits is 7200, while the sum is 32.

The square root of 28055921 is about 5296.7840242925. The cubic root of 28055921 is about 303.8609164385.

The spelling of 28055921 in words is "twenty-eight million, fifty-five thousand, nine hundred twenty-one".