21868539 has 32 divisors (see below), whose sum is σ = 37255680. Its totient is φ = 11078400.

The previous prime is 21868529. The next prime is 21868571. The reversal of 21868539 is 93586812.

It is not a de Polignac number, because 21868539 - 2¹² = 21864443 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21868539.

It is not an unprimeable number, because it can be changed into a prime (21868519) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8317 + ... + 10625.

It is an arithmetic number, because the mean of its divisors is an integer number (1164240).

Almost surely, 2^21868539 is an apocalyptic number.

21868539 is a deficient number, since it is larger than the sum of its proper divisors (15387141).

21868539 is a wasteful number, since it uses less digits than its factorization.

21868539 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2371.

The product of its digits is 103680, while the sum is 42.

The square root of 21868539 is about 4676.3809725043. The cubic root of 21868539 is about 279.6446981452.

The spelling of 21868539 in words is "twenty-one million, eight hundred sixty-eight thousand, five hundred thirty-nine".