21664411 has 4 divisors (see below), whose sum is σ = 21925512. Its totient is φ = 21403312.

The previous prime is 21664373. The next prime is 21664417. The reversal of 21664411 is 11446612.

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 21664411 - 2¹¹ = 21662363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21664417) 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, 130426 + ... + 130591.

It is an arithmetic number, because the mean of its divisors is an integer number (5481378).

Almost surely, 2^21664411 is an apocalyptic number.

21664411 is a deficient number, since it is larger than the sum of its proper divisors (261101).

21664411 is an equidigital number, since it uses as much as digits as its factorization.

21664411 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 261100.

The product of its digits is 1152, while the sum is 25.

The square root of 21664411 is about 4654.5043774821. The cubic root of 21664411 is about 278.7718788085.

The spelling of 21664411 in words is "twenty-one million, six hundred sixty-four thousand, four hundred eleven".