28021539 has 16 divisors (see below), whose sum is σ = 45984512. Its totient is φ = 14780448.

The previous prime is 28021531. The next prime is 28021579. The reversal of 28021539 is 93512082.

It is a happy number.

It is not a de Polignac number, because 28021539 - 2³ = 28021531 is a prime.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (28021531) 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 in 15 ways as a sum of consecutive naturals, for example, 51049 + ... + 51594.

It is an arithmetic number, because the mean of its divisors is an integer number (2874032).

Almost surely, 2^28021539 is an apocalyptic number.

28021539 is a deficient number, since it is larger than the sum of its proper divisors (17962973).

28021539 is a wasteful number, since it uses less digits than its factorization.

28021539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102666.

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 28021539 is about 5293.5374750728. The cubic root of 28021539 is about 303.7367404329.

The spelling of 28021539 in words is "twenty-eight million, twenty-one thousand, five hundred thirty-nine".