21664211997289 has 9 divisors (see below), whose sum is σ = 22025473819479. Its totient is φ = 21308781711960.

The previous prime is 21664211997283. The next prime is 21664211997301. The reversal of 21664211997289 is 98279911246612.

The square root of 21664211997289 is 4654483.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 704479884889 + 20959732112400 = 839333^2 + 4578180^2 .

It is not a de Polignac number, because 21664211997289 - 2¹⁷ = 21664211866217 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21664211997283) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 283885312 + ... + 283961614.

It is an arithmetic number, because the mean of its divisors is an integer number (2447274868831).

Almost surely, 2^{21664211997289} is an apocalyptic number.

21664211997289 is the 4654483-rd square number.

21664211997289 is the 2327242-nd centered octagonal number.

It is an amenable number.

21664211997289 is a deficient number, since it is larger than the sum of its proper divisors (361261822190).

21664211997289 is an frugal number, since it uses more digits than its factorization.

21664211997289 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 152728 (or 76364 counting only the distinct ones).

The product of its digits is 47029248, while the sum is 67.

The spelling of 21664211997289 in words is "twenty-one trillion, six hundred sixty-four billion, two hundred eleven million, nine hundred ninety-seven thousand, two hundred eighty-nine".