21604332 has 12 divisors (see below), whose sum is σ = 50410136. Its totient is φ = 7201440.

The previous prime is 21604327. The next prime is 21604339. The reversal of 21604332 is 23340612.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (12).

It is a super-2 number, since 2×21604332² = 933494322332448, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21604299 and 21604308.

It is not an unprimeable number, because it can be changed into a prime (21604339) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 900169 + ... + 900192.

Almost surely, 2^21604332 is an apocalyptic number.

It is an amenable number.

21604332 is an abundant number, since it is smaller than the sum of its proper divisors (28805804).

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

21604332 is a wasteful number, since it uses less digits than its factorization.

21604332 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1800368 (or 1800366 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 21.

The square root of 21604332 is about 4648.0460410801. The cubic root of 21604332 is about 278.5139467008.

Adding to 21604332 its reverse (23340612), we get a palindrome (44944944).

The spelling of 21604332 in words is "twenty-one million, six hundred four thousand, three hundred thirty-two".