28311921 has 12 divisors (see below), whose sum is σ = 44612880. Its totient is φ = 17158680.

The previous prime is 28311901. The next prime is 28311947. The reversal of 28311921 is 12911382.

It is a de Polignac number, because none of the positive numbers 2^k-28311921 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28311901) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 142891 + ... + 143088.

It is an arithmetic number, because the mean of its divisors is an integer number (3717740).

Almost surely, 2^28311921 is an apocalyptic number.

It is an amenable number.

28311921 is a deficient number, since it is larger than the sum of its proper divisors (16300959).

28311921 is a wasteful number, since it uses less digits than its factorization.

28311921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 285996 (or 285993 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 28311921 is about 5320.8947555839. The cubic root of 28311921 is about 304.7823260982.

The spelling of 28311921 in words is "twenty-eight million, three hundred eleven thousand, nine hundred twenty-one".