21664869 has 16 divisors (see below), whose sum is σ = 30096000. Its totient is φ = 13849920.

The previous prime is 21664861. The next prime is 21664879. The reversal of 21664869 is 96846612.

It is not a de Polignac number, because 21664869 - 2³ = 21664861 is a prime.

It is a super-2 number, since 2×21664869² = 938733097574322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21664869.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664861) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 6507 + ... + 9255.

It is an arithmetic number, because the mean of its divisors is an integer number (1881000).

Almost surely, 2^21664869 is an apocalyptic number.

It is an amenable number.

21664869 is a deficient number, since it is larger than the sum of its proper divisors (8431131).

21664869 is a wasteful number, since it uses less digits than its factorization.

21664869 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2860.

The product of its digits is 124416, while the sum is 42.

The square root of 21664869 is about 4654.5535768750. The cubic root of 21664869 is about 278.7738432687.

The spelling of 21664869 in words is "twenty-one million, six hundred sixty-four thousand, eight hundred sixty-nine".