28021439 has 4 divisors (see below), whose sum is σ = 28054920. Its totient is φ = 27987960.

The previous prime is 28021421. The next prime is 28021501. The reversal of 28021439 is 93412082.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 28021439 - 2⁸ = 28021183 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28021139) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15452 + ... + 17169.

It is an arithmetic number, because the mean of its divisors is an integer number (7013730).

Almost surely, 2^28021439 is an apocalyptic number.

28021439 is a deficient number, since it is larger than the sum of its proper divisors (33481).

28021439 is an equidigital number, since it uses as much as digits as its factorization.

28021439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33480.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 28021439 is about 5293.5280295848. The cubic root of 28021439 is about 303.7363791190.

The spelling of 28021439 in words is "twenty-eight million, twenty-one thousand, four hundred thirty-nine".