21664530 has 32 divisors (see below), whose sum is σ = 57772800. Its totient is φ = 5777136.

The previous prime is 21664529. The next prime is 21664607. The reversal of 21664530 is 3546612.

21664530 is a `hidden beast` number, since 2 + 16 + 645 + 3 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 21664494 and 21664503.

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, 39850 + ... + 40389.

It is an arithmetic number, because the mean of its divisors is an integer number (1805400).

Almost surely, 2^21664530 is an apocalyptic number.

21664530 is an abundant number, since it is smaller than the sum of its proper divisors (36108270).

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

21664530 is a wasteful number, since it uses less digits than its factorization.

21664530 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80255 (or 80249 counting only the distinct ones).

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

The square root of 21664530 is about 4654.5171607805. The cubic root of 21664530 is about 278.7723892277.

It can be divided in two parts, 216 and 64530, that added together give a palindrome (64746).

The spelling of 21664530 in words is "twenty-one million, six hundred sixty-four thousand, five hundred thirty".