12345666721 has 2 divisors, whose sum is σ = 12345666722. Its totient is φ = 12345666720.

The previous prime is 12345666677. The next prime is 12345666769. The reversal of 12345666721 is 12766654321.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 8056857600 + 4288809121 = 89760^2 + 65489^2 .

It is a cyclic number.

It is not a de Polignac number, because 12345666721 - 2⁹ = 12345666209 is a prime.

It is not a weakly prime, because it can be changed into another prime (12345667721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6172833360 + 6172833361.

It is an arithmetic number, because the mean of its divisors is an integer number (6172833361).

Almost surely, 2^12345666721 is an apocalyptic number.

It is an amenable number.

12345666721 is a deficient number, since it is larger than the sum of its proper divisors (1).

12345666721 is an equidigital number, since it uses as much as digits as its factorization.

12345666721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 362880, while the sum is 43.

The spelling of 12345666721 in words is "twelve billion, three hundred forty-five million, six hundred sixty-six thousand, seven hundred twenty-one".