18721664 has 32 divisors (see below), whose sum is σ = 40169640. Its totient is φ = 8640000.

The previous prime is 18721649. The next prime is 18721673. The reversal of 18721664 is 46612781.

It is a tau number, because it is divible by the number of its divisors (32).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3962 + ... + 7289.

Almost surely, 2^18721664 is an apocalyptic number.

It is an amenable number.

18721664 is an abundant number, since it is smaller than the sum of its proper divisors (21447976).

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

18721664 is a wasteful number, since it uses less digits than its factorization.

18721664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11278 (or 11266 counting only the distinct ones).

The product of its digits is 16128, while the sum is 35.

The square root of 18721664 is about 4326.8538223518. The cubic root of 18721664 is about 265.5307459638.

The spelling of 18721664 in words is "eighteen million, seven hundred twenty-one thousand, six hundred sixty-four".