28521239 has 4 divisors (see below), whose sum is σ = 29504760. Its totient is φ = 27537720.

The previous prime is 28521217. The next prime is 28521247. The reversal of 28521239 is 93212582.

It is a happy number.

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 28521239 - 2⁸ = 28520983 is a prime.

It is a super-2 number, since 2×28521239² = 1626922148190242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28521139) 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, 491717 + ... + 491774.

It is an arithmetic number, because the mean of its divisors is an integer number (7376190).

Almost surely, 2^28521239 is an apocalyptic number.

28521239 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

28521239 is a deficient number, since it is larger than the sum of its proper divisors (983521).

28521239 is an equidigital number, since it uses as much as digits as its factorization.

28521239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 983520.

The product of its digits is 8640, while the sum is 32.

The square root of 28521239 is about 5340.5279701543. The cubic root of 28521239 is about 305.5315964366.

The spelling of 28521239 in words is "twenty-eight million, five hundred twenty-one thousand, two hundred thirty-nine".