6561881656 has 16 divisors (see below), whose sum is σ = 13422030840. Its totient is φ = 2982673440.

The previous prime is 6561881653. The next prime is 6561881659.

6561881656 is nontrivially palindromic in base 10.

It is an interprime number because it is at equal distance from previous prime (6561881653) and next prime (6561881659).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6561881653) 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 in 3 ways as a sum of consecutive naturals, for example, 37283331 + ... + 37283506.

Almost surely, 2^6561881656 is an apocalyptic number.

It is an amenable number.

6561881656 is an abundant number, since it is smaller than the sum of its proper divisors (6860149184).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

6561881656 is a wasteful number, since it uses less digits than its factorization.

6561881656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74566854 (or 74566850 counting only the distinct ones).

The product of its digits is 2073600, while the sum is 52.

The square root of 6561881656 is about 81005.4421381675. The cubic root of 6561881656 is about 1872.1592924268.

The spelling of 6561881656 in words is "six billion, five hundred sixty-one million, eight hundred eighty-one thousand, six hundred fifty-six".