21664605465 has 24 divisors (see below), whose sum is σ = 38942799168. Its totient is φ = 11554455600.

The previous prime is 21664605461. The next prime is 21664605481. The reversal of 21664605465 is 56450646612.

21664605465 is a `hidden beast` number, since 2 + 1 + 66 + 46 + 0 + 546 + 5 = 666.

It is not a de Polignac number, because 21664605465 - 2² = 21664605461 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21664605465.

It is not an unprimeable number, because it can be changed into a prime (21664605461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8914261 + ... + 8916690.

It is an arithmetic number, because the mean of its divisors is an integer number (1622616632).

Almost surely, 2^21664605465 is an apocalyptic number.

It is an amenable number.

21664605465 is a deficient number, since it is larger than the sum of its proper divisors (17278193703).

21664605465 is an equidigital number, since it uses as much as digits as its factorization.

21664605465 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17830971 (or 17830959 counting only the distinct ones).

The product of its (nonzero) digits is 1036800, while the sum is 45.

The spelling of 21664605465 in words is "twenty-one billion, six hundred sixty-four million, six hundred five thousand, four hundred sixty-five".