12644035721 has 4 divisors (see below), whose sum is σ = 12644380944. Its totient is φ = 12643690500.

The previous prime is 12644035693. The next prime is 12644035777. The reversal of 12644035721 is 12753044621.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12753044621 = 709 ⋅17987369.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12644035721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12644035121) 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, 110135 + ... + 193436.

It is an arithmetic number, because the mean of its divisors is an integer number (3161095236).

Almost surely, 2^12644035721 is an apocalyptic number.

It is an amenable number.

12644035721 is a deficient number, since it is larger than the sum of its proper divisors (345223).

12644035721 is an equidigital number, since it uses as much as digits as its factorization.

12644035721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345222.

The product of its (nonzero) digits is 40320, while the sum is 35.

The spelling of 12644035721 in words is "twelve billion, six hundred forty-four million, thirty-five thousand, seven hundred twenty-one".