21316668 has 12 divisors (see below), whose sum is σ = 49738920. Its totient is φ = 7105552.

The previous prime is 21316667. The next prime is 21316693. The reversal of 21316668 is 86661312.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21316661) 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, 888183 + ... + 888206.

It is an arithmetic number, because the mean of its divisors is an integer number (4144910).

Almost surely, 2^21316668 is an apocalyptic number.

It is an amenable number.

21316668 is an abundant number, since it is smaller than the sum of its proper divisors (28422252).

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

21316668 is a wasteful number, since it uses less digits than its factorization.

21316668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1776396 (or 1776394 counting only the distinct ones).

The product of its digits is 10368, while the sum is 33.

The square root of 21316668 is about 4616.9977257954. The cubic root of 21316668 is about 277.2722715717.

The spelling of 21316668 in words is "twenty-one million, three hundred sixteen thousand, six hundred sixty-eight".