28319921 has 16 divisors (see below), whose sum is σ = 34045440. Its totient is φ = 23042880.

The previous prime is 28319891. The next prime is 28319933. The reversal of 28319921 is 12991382.

28319921 is nontrivially palindromic in base 16.

It is a de Polignac number, because none of the positive numbers 2^k-28319921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28319981) 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, 11240 + ... + 13526.

It is an arithmetic number, because the mean of its divisors is an integer number (2127840).

Almost surely, 2^28319921 is an apocalyptic number.

It is an amenable number.

28319921 is a deficient number, since it is larger than the sum of its proper divisors (5725519).

28319921 is a wasteful number, since it uses less digits than its factorization.

28319921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2384.

The product of its digits is 7776, while the sum is 35.

The square root of 28319921 is about 5321.6464557503. The cubic root of 28319921 is about 304.8110304849.

The spelling of 28319921 in words is "twenty-eight million, three hundred nineteen thousand, nine hundred twenty-one".