21845565 has 32 divisors (see below), whose sum is σ = 44386560. Its totient is φ = 9986112.

The previous prime is 21845563. The next prime is 21845597. The reversal of 21845565 is 56554812.

21845565 is a `hidden beast` number, since 21 + 84 + 556 + 5 = 666.

It is not a de Polignac number, because 21845565 - 2¹ = 21845563 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21845563) 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, 10614 + ... + 12503.

It is an arithmetic number, because the mean of its divisors is an integer number (1387080).

Almost surely, 2^21845565 is an apocalyptic number.

It is an amenable number.

21845565 is an abundant number, since it is smaller than the sum of its proper divisors (22540995).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21845565 is a wasteful number, since it uses less digits than its factorization.

21845565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23138 (or 23132 counting only the distinct ones).

The product of its digits is 48000, while the sum is 36.

The square root of 21845565 is about 4673.9239403311. The cubic root of 21845565 is about 279.5467368931.

The spelling of 21845565 in words is "twenty-one million, eight hundred forty-five thousand, five hundred sixty-five".