28109021 has 2 divisors, whose sum is σ = 28109022. Its totient is φ = 28109020.

The previous prime is 28108991. The next prime is 28109023. The reversal of 28109021 is 12090182.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 24552025 + 3556996 = 4955^2 + 1886^2 .

It is a cyclic number.

It is not a de Polignac number, because 28109021 - 2¹⁸ = 27846877 is a prime.

Together with 28109023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28109023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14054510 + 14054511.

It is an arithmetic number, because the mean of its divisors is an integer number (14054511).

Almost surely, 2^28109021 is an apocalyptic number.

It is an amenable number.

28109021 is a deficient number, since it is larger than the sum of its proper divisors (1).

28109021 is an equidigital number, since it uses as much as digits as its factorization.

28109021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 23.

The square root of 28109021 is about 5301.7941302921. The cubic root of 28109021 is about 304.0524962723.

The spelling of 28109021 in words is "twenty-eight million, one hundred nine thousand, twenty-one".