6561551656 has 64 divisors (see below), whose sum is σ = 14190264000. Its totient is φ = 2813045760.

The previous prime is 6561551653. The next prime is 6561551657.

6561551656 is nontrivially palindromic in base 10.

It is a hoax number, since the sum of its digits (46) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (6561551651) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 374320 + ... + 391456.

It is an arithmetic number, because the mean of its divisors is an integer number (221722875).

Almost surely, 2^6561551656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6561551656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (7095132000).

6561551656 is an abundant number, since it is smaller than the sum of its proper divisors (7628712344).

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

6561551656 is a wasteful number, since it uses less digits than its factorization.

6561551656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17402 (or 17398 counting only the distinct ones).

The product of its digits is 810000, while the sum is 46.

The square root of 6561551656 is about 81003.4052123736. The cubic root of 6561551656 is about 1872.1279079878.

The spelling of 6561551656 in words is "six billion, five hundred sixty-one million, five hundred fifty-one thousand, six hundred fifty-six".