21864645 has 24 divisors (see below), whose sum is σ = 41344992. Its totient is φ = 10600800.

The previous prime is 21864617. The next prime is 21864653. The reversal of 21864645 is 54646812.

21864645 is a `hidden beast` number, since 2 + 1 + 8 + 6 + 4 + 645 = 666.

It is not a de Polignac number, because 21864645 - 2⁵ = 21864613 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 21591 + ... + 22580.

It is an arithmetic number, because the mean of its divisors is an integer number (1722708).

Almost surely, 2^21864645 is an apocalyptic number.

It is an amenable number.

21864645 is a deficient number, since it is larger than the sum of its proper divisors (19480347).

21864645 is a wasteful number, since it uses less digits than its factorization.

21864645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44193 (or 44190 counting only the distinct ones).

The product of its digits is 46080, while the sum is 36.

The square root of 21864645 is about 4675.9646063673. The cubic root of 21864645 is about 279.6280989401.

The spelling of 21864645 in words is "twenty-one million, eight hundred sixty-four thousand, six hundred forty-five".