28228921 has 4 divisors (see below), whose sum is σ = 32261632. Its totient is φ = 24196212.

The previous prime is 28228897. The next prime is 28228933. The reversal of 28228921 is 12982282.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 28228921 - 2¹⁵ = 28196153 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (28228021) 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, 2016345 + ... + 2016358.

It is an arithmetic number, because the mean of its divisors is an integer number (8065408).

Almost surely, 2^28228921 is an apocalyptic number.

It is an amenable number.

28228921 is a deficient number, since it is larger than the sum of its proper divisors (4032711).

28228921 is an equidigital number, since it uses as much as digits as its factorization.

28228921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4032710.

The product of its digits is 9216, while the sum is 34.

The square root of 28228921 is about 5313.0895908125. The cubic root of 28228921 is about 304.4841985144.

The spelling of 28228921 in words is "twenty-eight million, two hundred twenty-eight thousand, nine hundred twenty-one".