12811749721 has 3 divisors (see below), whose sum is σ = 12811862911. Its totient is φ = 12811636532.

The previous prime is 12811749701. The next prime is 12811749737. The reversal of 12811749721 is 12794711821.

The square root of 12811749721 is 113189.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 5308725321 + 7503024400 = 72861^2 + 86620^2 .

It is not a de Polignac number, because 12811749721 - 2²⁵ = 12778195289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12811749701) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 56595 + ... + 169783.

Almost surely, 2^12811749721 is an apocalyptic number.

12811749721 is the 113189-th square number.

12811749721 is the 56595-th centered octagonal number.

It is an amenable number.

12811749721 is a deficient number, since it is larger than the sum of its proper divisors (113190).

12811749721 is an frugal number, since it uses more digits than its factorization.

12811749721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 226378 (or 113189 counting only the distinct ones).

The product of its digits is 56448, while the sum is 43.

The spelling of 12811749721 in words is "twelve billion, eight hundred eleven million, seven hundred forty-nine thousand, seven hundred twenty-one".