21082168809 has 135 divisors (see below), whose sum is σ = 36729059103. Its totient is φ = 12043219968.

The previous prime is 21082168733. The next prime is 21082168829. The reversal of 21082168809 is 90886128012.

It is a happy number.

The square root of 21082168809 is 145197.

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

It can be written as a sum of positive squares in 13 ways, for example, as 11116539225 + 9965629584 = 105435^2 + 99828^2 .

It is not a de Polignac number, because 21082168809 - 2¹⁵ = 21082136041 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21082168829) by changing a digit.

It is a polite number, since it can be written in 134 ways as a sum of consecutive naturals, for example, 288796797 + ... + 288796869.

Almost surely, 2^21082168809 is an apocalyptic number.

21082168809 is the 145197-th square number.

21082168809 is the 72599-th centered octagonal number.

It is an amenable number.

21082168809 is a deficient number, since it is larger than the sum of its proper divisors (15646890294).

21082168809 is an equidigital number, since it uses as much as digits as its factorization.

21082168809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 218 (or 106 counting only the distinct ones).

The product of its (nonzero) digits is 110592, while the sum is 45.

It can be divided in two parts, 2108216 and 8809, that added together give a square (2117025 = 1455²).

The spelling of 21082168809 in words is "twenty-one billion, eighty-two million, one hundred sixty-eight thousand, eight hundred nine".