6656120656721 has 4 divisors (see below), whose sum is σ = 6694595342772. Its totient is φ = 6617645970672.

The previous prime is 6656120656711. The next prime is 6656120656733. The reversal of 6656120656721 is 1276560216566.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3646724929600 + 3009395727121 = 1909640^2 + 1734761^2 .

It is a cyclic number.

It is not a de Polignac number, because 6656120656721 - 2¹⁸ = 6656120394577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6656120656711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19237342766 + ... + 19237343111.

It is an arithmetic number, because the mean of its divisors is an integer number (1673648835693).

Almost surely, 2^{6656120656721} is an apocalyptic number.

It is an amenable number.

6656120656721 is a deficient number, since it is larger than the sum of its proper divisors (38474686051).

6656120656721 is a wasteful number, since it uses less digits than its factorization.

6656120656721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38474686050.

The product of its (nonzero) digits is 5443200, while the sum is 53.

The spelling of 6656120656721 in words is "six trillion, six hundred fifty-six billion, one hundred twenty million, six hundred fifty-six thousand, seven hundred twenty-one".