28173521 has 4 divisors (see below), whose sum is σ = 28635444. Its totient is φ = 27711600.

The previous prime is 28173511. The next prime is 28173527. The reversal of 28173521 is 12537182.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1537600 + 26635921 = 1240^2 + 5161^2 .

It is a cyclic number.

It is not a de Polignac number, because 28173521 - 2¹⁴ = 28157137 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (28173527) 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, 230870 + ... + 230991.

It is an arithmetic number, because the mean of its divisors is an integer number (7158861).

Almost surely, 2^28173521 is an apocalyptic number.

It is an amenable number.

28173521 is a deficient number, since it is larger than the sum of its proper divisors (461923).

28173521 is an equidigital number, since it uses as much as digits as its factorization.

28173521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 461922.

The product of its digits is 3360, while the sum is 29.

The square root of 28173521 is about 5307.8734913334. The cubic root of 28173521 is about 304.2848819866.

The spelling of 28173521 in words is "twenty-eight million, one hundred seventy-three thousand, five hundred twenty-one".