21616664 has 8 divisors (see below), whose sum is σ = 40531260. Its totient is φ = 10808328.

The previous prime is 21616657. The next prime is 21616669. The reversal of 21616664 is 46661612.

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 21616664.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21616669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1351034 + ... + 1351049.

Almost surely, 2^21616664 is an apocalyptic number.

It is an amenable number.

21616664 is a deficient number, since it is larger than the sum of its proper divisors (18914596).

21616664 is a wasteful number, since it uses less digits than its factorization.

21616664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2702089 (or 2702085 counting only the distinct ones).

The product of its digits is 10368, while the sum is 32.

The square root of 21616664 is about 4649.3724307696. The cubic root of 21616664 is about 278.5669296039.

The spelling of 21616664 in words is "twenty-one million, six hundred sixteen thousand, six hundred sixty-four".