21664511 has 8 divisors (see below), whose sum is σ = 25024464. Its totient is φ = 18536320.

The previous prime is 21664507. The next prime is 21664529. The reversal of 21664511 is 11546612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21664511 - 2² = 21664507 is a prime.

It is a super-3 number, since 3×21664511³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664501) 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, 57740 + ... + 58113.

It is an arithmetic number, because the mean of its divisors is an integer number (3128058).

Almost surely, 2^21664511 is an apocalyptic number.

21664511 is a deficient number, since it is larger than the sum of its proper divisors (3359953).

21664511 is a wasteful number, since it uses less digits than its factorization.

21664511 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115881.

The product of its digits is 1440, while the sum is 26.

The square root of 21664511 is about 4654.5151197520. The cubic root of 21664511 is about 278.7723077323.

The spelling of 21664511 in words is "twenty-one million, six hundred sixty-four thousand, five hundred eleven".