21205668 has 24 divisors (see below), whose sum is σ = 53978400. Its totient is φ = 6425920.

The previous prime is 21205663. The next prime is 21205687. The reversal of 21205668 is 86650212.

It is not an unprimeable number, because it can be changed into a prime (21205661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 80193 + ... + 80456.

It is an arithmetic number, because the mean of its divisors is an integer number (2249100).

Almost surely, 2^21205668 is an apocalyptic number.

It is an amenable number.

21205668 is an abundant number, since it is smaller than the sum of its proper divisors (32772732).

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

21205668 is a wasteful number, since it uses less digits than its factorization.

21205668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160667 (or 160665 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 21205668 is about 4604.9612376219. The cubic root of 21205668 is about 276.7901637332.

The spelling of 21205668 in words is "twenty-one million, two hundred five thousand, six hundred sixty-eight".