28820221 has 2 divisors, whose sum is σ = 28820222. Its totient is φ = 28820220.

The previous prime is 28820179. The next prime is 28820263. The reversal of 28820221 is 12202882.

It is a balanced prime because it is at equal distance from previous prime (28820179) and next prime (28820263).

It can be written as a sum of positive squares in only one way, i.e., 14907321 + 13912900 = 3861^2 + 3730^2 .

It is a cyclic number.

It is not a de Polignac number, because 28820221 - 2²¹ = 26723069 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28820291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14410110 + 14410111.

It is an arithmetic number, because the mean of its divisors is an integer number (14410111).

Almost surely, 2^28820221 is an apocalyptic number.

It is an amenable number.

28820221 is a deficient number, since it is larger than the sum of its proper divisors (1).

28820221 is an equidigital number, since it uses as much as digits as its factorization.

28820221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1024, while the sum is 25.

The square root of 28820221 is about 5368.4467958619. The cubic root of 28820221 is about 306.5954947995.

The spelling of 28820221 in words is "twenty-eight million, eight hundred twenty thousand, two hundred twenty-one".