21664212 has 24 divisors (see below), whose sum is σ = 50668800. Its totient is φ = 7204416.

The previous prime is 21664207. The next prime is 21664267. The reversal of 21664212 is 21246612.

It is a nude number because it is divisible by every one of its digits.

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 7 ways as a sum of consecutive naturals, for example, 3864 + ... + 7632.

It is an arithmetic number, because the mean of its divisors is an integer number (2111200).

Almost surely, 2^21664212 is an apocalyptic number.

It is an amenable number.

21664212 is an abundant number, since it is smaller than the sum of its proper divisors (29004588).

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

21664212 is a wasteful number, since it uses less digits than its factorization.

21664212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4255 (or 4253 counting only the distinct ones).

The product of its digits is 1152, while the sum is 24.

The square root of 21664212 is about 4654.4830002912. The cubic root of 21664212 is about 278.7710252462.

The spelling of 21664212 in words is "twenty-one million, six hundred sixty-four thousand, two hundred twelve".