21604365 has 48 divisors (see below), whose sum is σ = 40974336. Its totient is φ = 10483200.

The previous prime is 21604339. The next prime is 21604369. The reversal of 21604365 is 56340612.

21604365 is a `hidden beast` number, since 21 + 604 + 36 + 5 = 666.

It is not a de Polignac number, because 21604365 - 2⁶ = 21604301 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21604369) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 23260 + ... + 24170.

It is an arithmetic number, because the mean of its divisors is an integer number (853632).

Almost surely, 2^21604365 is an apocalyptic number.

It is an amenable number.

21604365 is a deficient number, since it is larger than the sum of its proper divisors (19369971).

21604365 is a wasteful number, since it uses less digits than its factorization.

21604365 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 970 (or 967 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 21604365 is about 4648.0495909575. The cubic root of 21604365 is about 278.5140885081.

Adding to 21604365 its reverse (56340612), we get a palindrome (77944977).

The spelling of 21604365 in words is "twenty-one million, six hundred four thousand, three hundred sixty-five".