28891021 has 2 divisors, whose sum is σ = 28891022. Its totient is φ = 28891020.

The previous prime is 28890997. The next prime is 28891069. The reversal of 28891021 is 12019882.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 26522500 + 2368521 = 5150^2 + 1539^2 .

It is a cyclic number.

It is not a de Polignac number, because 28891021 - 2⁷ = 28890893 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28891081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14445510 + 14445511.

It is an arithmetic number, because the mean of its divisors is an integer number (14445511).

Almost surely, 2^28891021 is an apocalyptic number.

It is an amenable number.

28891021 is a deficient number, since it is larger than the sum of its proper divisors (1).

28891021 is an equidigital number, since it uses as much as digits as its factorization.

28891021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 28891021 is about 5375.0368370831. The cubic root of 28891021 is about 306.8463511928.

The spelling of 28891021 in words is "twenty-eight million, eight hundred ninety-one thousand, twenty-one".