28668221 has 2 divisors, whose sum is σ = 28668222. Its totient is φ = 28668220.

The previous prime is 28668217. The next prime is 28668247. The reversal of 28668221 is 12286682.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 23145721 + 5522500 = 4811^2 + 2350^2 .

It is a cyclic number.

It is not a de Polignac number, because 28668221 - 2² = 28668217 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28668421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14334110 + 14334111.

It is an arithmetic number, because the mean of its divisors is an integer number (14334111).

Almost surely, 2^28668221 is an apocalyptic number.

It is an amenable number.

28668221 is a deficient number, since it is larger than the sum of its proper divisors (1).

28668221 is an equidigital number, since it uses as much as digits as its factorization.

28668221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18432, while the sum is 35.

The square root of 28668221 is about 5354.2712856186. The cubic root of 28668221 is about 306.0555419137.

The spelling of 28668221 in words is "twenty-eight million, six hundred sixty-eight thousand, two hundred twenty-one".