21691288169 has 4 divisors (see below), whose sum is σ = 22220344020. Its totient is φ = 21162232320.

The previous prime is 21691288153. The next prime is 21691288183. The reversal of 21691288169 is 96188219612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 706868569 + 20984419600 = 26587^2 + 144860^2 .

It is a cyclic number.

It is not a de Polignac number, because 21691288169 - 2⁴ = 21691288153 is a prime.

It is a super-2 number, since 2×21691288169² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

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 21691288169.

It is not an unprimeable number, because it can be changed into a prime (21691288139) 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 3 ways as a sum of consecutive naturals, for example, 264527864 + ... + 264527945.

It is an arithmetic number, because the mean of its divisors is an integer number (5555086005).

Almost surely, 2^21691288169 is an apocalyptic number.

It is an amenable number.

21691288169 is a deficient number, since it is larger than the sum of its proper divisors (529055851).

21691288169 is an equidigital number, since it uses as much as digits as its factorization.

21691288169 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 529055850.

The product of its digits is 746496, while the sum is 53.

The spelling of 21691288169 in words is "twenty-one billion, six hundred ninety-one million, two hundred eighty-eight thousand, one hundred sixty-nine".