21308116729 has 9 divisors (see below), whose sum is σ = 21672213069. Its totient is φ = 20950044960.

The previous prime is 21308116703. The next prime is 21308116733. The reversal of 21308116729 is 92761180312.

The square root of 21308116729 is 145973.

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

It can be written as a sum of positive squares in 4 ways, for example, as 19122741225 + 2185375504 = 138285^2 + 46748^2 .

It is not a de Polignac number, because 21308116729 - 2¹³ = 21308108537 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21308116691 and 21308116700.

It is not an unprimeable number, because it can be changed into a prime (21308116229) 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 8 ways as a sum of consecutive naturals, for example, 8903157 + ... + 8905549.

Almost surely, 2^21308116729 is an apocalyptic number.

21308116729 is the 145973-rd square number.

21308116729 is the 72987-th centered octagonal number.

It is an amenable number.

21308116729 is a deficient number, since it is larger than the sum of its proper divisors (364096340).

21308116729 is an frugal number, since it uses more digits than its factorization.

21308116729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4908 (or 2454 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 40.

The spelling of 21308116729 in words is "twenty-one billion, three hundred eight million, one hundred sixteen thousand, seven hundred twenty-nine".