28921321 has 16 divisors (see below), whose sum is σ = 34151040. Its totient is φ = 24145920.

The previous prime is 28921307. The next prime is 28921337. The reversal of 28921321 is 12312982.

It is the 2196-th star number.

It is a cyclic number.

It is not a de Polignac number, because 28921321 - 2⁵ = 28921289 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 28921321.

It is not an unprimeable number, because it can be changed into a prime (28924321) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37225 + ... + 37993.

It is an arithmetic number, because the mean of its divisors is an integer number (2134440).

Almost surely, 2^28921321 is an apocalyptic number.

It is an amenable number.

28921321 is a deficient number, since it is larger than the sum of its proper divisors (5229719).

28921321 is a wasteful number, since it uses less digits than its factorization.

28921321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1056.

The product of its digits is 1728, while the sum is 28.

The square root of 28921321 is about 5377.8546837935. The cubic root of 28921321 is about 306.9535840022.

The spelling of 28921321 in words is "twenty-eight million, nine hundred twenty-one thousand, three hundred twenty-one".