28249921 has 6 divisors (see below), whose sum is σ = 32862210. Its totient is φ = 24214176.

The previous prime is 28249919. The next prime is 28249939. The reversal of 28249921 is 12994282.

It can be written as a sum of positive squares in only one way, i.e., 27709696 + 540225 = 5264^2 + 735^2 .

It is not a de Polignac number, because 28249921 - 2¹ = 28249919 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28249621) 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 5 ways as a sum of consecutive naturals, for example, 288216 + ... + 288313.

It is an arithmetic number, because the mean of its divisors is an integer number (5477035).

Almost surely, 2^28249921 is an apocalyptic number.

It is an amenable number.

28249921 is a deficient number, since it is larger than the sum of its proper divisors (4612289).

28249921 is an equidigital number, since it uses as much as digits as its factorization.

28249921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 576543 (or 576536 counting only the distinct ones).

The product of its digits is 20736, while the sum is 37.

The square root of 28249921 is about 5315.0654746673. The cubic root of 28249921 is about 304.5596835491.

The spelling of 28249921 in words is "twenty-eight million, two hundred forty-nine thousand, nine hundred twenty-one".