12721809681 has 81 divisors (see below), whose sum is σ = 22078716699. Its totient is φ = 7038158400.

The previous prime is 12721809671. The next prime is 12721809701. The reversal of 12721809681 is 18690812721.

The square root of 12721809681 is 112791.

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

12721809681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 613008081 + 12108801600 = 24759^2 + 110040^2 .

It is not a de Polignac number, because 12721809681 - 2⁹ = 12721809169 is a prime.

It is a super-2 number, since 2×12721809681² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (12721809671) 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 80 ways as a sum of consecutive naturals, for example, 97112986 + ... + 97113116.

Almost surely, 2^12721809681 is an apocalyptic number.

12721809681 is the 112791-st square number.

12721809681 is the 56396-th centered octagonal number.

It is an amenable number.

12721809681 is a deficient number, since it is larger than the sum of its proper divisors (9356907018).

12721809681 is an equidigital number, since it uses as much as digits as its factorization.

12721809681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 364 (or 182 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 45.

The spelling of 12721809681 in words is "twelve billion, seven hundred twenty-one million, eight hundred nine thousand, six hundred eighty-one".