21840539 has 4 divisors (see below), whose sum is σ = 24960624. Its totient is φ = 18720456.

The previous prime is 21840521. The next prime is 21840541. The reversal of 21840539 is 93504812.

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 21840539 - 2⁸ = 21840283 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21843539) 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, 1560032 + ... + 1560045.

It is an arithmetic number, because the mean of its divisors is an integer number (6240156).

Almost surely, 2^21840539 is an apocalyptic number.

21840539 is a deficient number, since it is larger than the sum of its proper divisors (3120085).

21840539 is an equidigital number, since it uses as much as digits as its factorization.

21840539 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3120084.

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

The square root of 21840539 is about 4673.3862455397. The cubic root of 21840539 is about 279.5252968486.

The spelling of 21840539 in words is "twenty-one million, eight hundred forty thousand, five hundred thirty-nine".