28358221 has 4 divisors (see below), whose sum is σ = 28420732. Its totient is φ = 28295712.

The previous prime is 28358191. The next prime is 28358257. The reversal of 28358221 is 12285382.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17724100 + 10634121 = 4210^2 + 3261^2 .

It is a cyclic number.

It is not a de Polignac number, because 28358221 - 2⁷ = 28358093 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 (28358321) 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 3 ways as a sum of consecutive naturals, for example, 30570 + ... + 31483.

It is an arithmetic number, because the mean of its divisors is an integer number (7105183).

Almost surely, 2^28358221 is an apocalyptic number.

It is an amenable number.

28358221 is a deficient number, since it is larger than the sum of its proper divisors (62511).

28358221 is an equidigital number, since it uses as much as digits as its factorization.

28358221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62510.

The product of its digits is 7680, while the sum is 31.

The square root of 28358221 is about 5325.2437502897. The cubic root of 28358221 is about 304.9483778977.

The spelling of 28358221 in words is "twenty-eight million, three hundred fifty-eight thousand, two hundred twenty-one".