28187021 has 2 divisors, whose sum is σ = 28187022. Its totient is φ = 28187020.

The previous prime is 28187009. The next prime is 28187039. The reversal of 28187021 is 12078182.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21031396 + 7155625 = 4586^2 + 2675^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28187021 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 (28187041) 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 as a sum of consecutive naturals, namely, 14093510 + 14093511.

It is an arithmetic number, because the mean of its divisors is an integer number (14093511).

Almost surely, 2^28187021 is an apocalyptic number.

It is an amenable number.

28187021 is a deficient number, since it is larger than the sum of its proper divisors (1).

28187021 is an equidigital number, since it uses as much as digits as its factorization.

28187021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 28187021 is about 5309.1450347490. The cubic root of 28187021 is about 304.3334759596. Note that the first 3 decimals are identical.

The spelling of 28187021 in words is "twenty-eight million, one hundred eighty-seven thousand, twenty-one".