21664120 has 32 divisors (see below), whose sum is σ = 51613200. Its totient is φ = 8155648.

The previous prime is 21664117. The next prime is 21664141. The reversal of 21664120 is 2146612.

It is a junction number, because it is equal to n+sod(n) for n = 21664091 and 21664100.

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, 15250 + ... + 16609.

Almost surely, 2^21664120 is an apocalyptic number.

21664120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21664120 is an abundant number, since it is smaller than the sum of its proper divisors (29949080).

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

21664120 is a wasteful number, since it uses less digits than its factorization.

21664120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31887 (or 31883 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21664120 is about 4654.4731173356. The cubic root of 21664120 is about 278.7706306327.

The spelling of 21664120 in words is "twenty-one million, six hundred sixty-four thousand, one hundred twenty".