21664059 has 4 divisors (see below), whose sum is σ = 28885416. Its totient is φ = 14442704.

The previous prime is 21664051. The next prime is 21664063. The reversal of 21664059 is 95046612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21664059 - 2³ = 21664051 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21664051) 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, 3610674 + ... + 3610679.

It is an arithmetic number, because the mean of its divisors is an integer number (7221354).

Almost surely, 2^21664059 is an apocalyptic number.

21664059 is a deficient number, since it is larger than the sum of its proper divisors (7221357).

21664059 is an equidigital number, since it uses as much as digits as its factorization.

21664059 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7221356.

The product of its (nonzero) digits is 12960, while the sum is 33.

The square root of 21664059 is about 4654.4665644948. The cubic root of 21664059 is about 278.7703689862.

The spelling of 21664059 in words is "twenty-one million, six hundred sixty-four thousand, fifty-nine".