21864805 has 16 divisors (see below), whose sum is σ = 28180224. Its totient is φ = 16226560.

The previous prime is 21864797. The next prime is 21864853. The reversal of 21864805 is 50846812.

It is not a de Polignac number, because 21864805 - 2³ = 21864797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4224 + ... + 7846.

It is an arithmetic number, because the mean of its divisors is an integer number (1761264).

Almost surely, 2^21864805 is an apocalyptic number.

It is an amenable number.

21864805 is a deficient number, since it is larger than the sum of its proper divisors (6315419).

21864805 is a wasteful number, since it uses less digits than its factorization.

21864805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3716.

The product of its (nonzero) digits is 15360, while the sum is 34.

The square root of 21864805 is about 4675.9817151054. The cubic root of 21864805 is about 279.6287810212.

The spelling of 21864805 in words is "twenty-one million, eight hundred sixty-four thousand, eight hundred five".