21184664 has 8 divisors (see below), whose sum is σ = 39721260. Its totient is φ = 10592328.

The previous prime is 21184661. The next prime is 21184699. The reversal of 21184664 is 46648112.

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21184664.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21184661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1324034 + ... + 1324049.

Almost surely, 2^21184664 is an apocalyptic number.

It is an amenable number.

21184664 is a deficient number, since it is larger than the sum of its proper divisors (18536596).

21184664 is a wasteful number, since it uses less digits than its factorization.

21184664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2648089 (or 2648085 counting only the distinct ones).

The product of its digits is 9216, while the sum is 32.

The square root of 21184664 is about 4602.6800888178. The cubic root of 21184664 is about 276.6987475904.

The spelling of 21184664 in words is "twenty-one million, one hundred eighty-four thousand, six hundred sixty-four".