13781262721 has 4 divisors (see below), whose sum is σ = 14591925252. Its totient is φ = 12970600192.

The previous prime is 13781262697. The next prime is 13781262767. The reversal of 13781262721 is 12726218731.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12726218731 = 28627 ⋅444553.

It can be written as a sum of positive squares in 2 ways, for example, as 12548480400 + 1232782321 = 112020^2 + 35111^2 .

It is a cyclic number.

It is not a de Polignac number, because 13781262721 - 2²³ = 13772874113 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13781262221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 405331240 + ... + 405331273.

It is an arithmetic number, because the mean of its divisors is an integer number (3647981313).

Almost surely, 2^13781262721 is an apocalyptic number.

It is an amenable number.

13781262721 is a deficient number, since it is larger than the sum of its proper divisors (810662531).

13781262721 is an equidigital number, since it uses as much as digits as its factorization.

13781262721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 810662530.

The product of its digits is 56448, while the sum is 40.

The spelling of 13781262721 in words is "thirteen billion, seven hundred eighty-one million, two hundred sixty-two thousand, seven hundred twenty-one".