21856845 has 16 divisors (see below), whose sum is σ = 35565120. Its totient is φ = 11458944.

The previous prime is 21856837. The next prime is 21856847. The reversal of 21856845 is 54865812.

It is not a de Polignac number, because 21856845 - 2³ = 21856837 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21856847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11464 + ... + 13233.

It is an arithmetic number, because the mean of its divisors is an integer number (2222820).

Almost surely, 2^21856845 is an apocalyptic number.

It is an amenable number.

21856845 is a deficient number, since it is larger than the sum of its proper divisors (13708275).

21856845 is a wasteful number, since it uses less digits than its factorization.

21856845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24764.

The product of its digits is 76800, while the sum is 39.

The square root of 21856845 is about 4675.1304794626. The cubic root of 21856845 is about 279.5948434480.

The spelling of 21856845 in words is "twenty-one million, eight hundred fifty-six thousand, eight hundred forty-five".