11643657721 has 2 divisors, whose sum is σ = 11643657722. Its totient is φ = 11643657720.

The previous prime is 11643657719. The next prime is 11643657749. The reversal of 11643657721 is 12775634611.

11643657721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10047255696 + 1596402025 = 100236^2 + 39955^2 .

It is a cyclic number.

It is not a de Polignac number, because 11643657721 - 2¹ = 11643657719 is a prime.

Together with 11643657719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (11643652721) 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 as a sum of consecutive naturals, namely, 5821828860 + 5821828861.

It is an arithmetic number, because the mean of its divisors is an integer number (5821828861).

Almost surely, 2^11643657721 is an apocalyptic number.

It is an amenable number.

11643657721 is a deficient number, since it is larger than the sum of its proper divisors (1).

11643657721 is an equidigital number, since it uses as much as digits as its factorization.

11643657721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 211680, while the sum is 43.

The spelling of 11643657721 in words is "eleven billion, six hundred forty-three million, six hundred fifty-seven thousand, seven hundred twenty-one".