6561644556 has 12 divisors (see below), whose sum is σ = 15310503992. Its totient is φ = 2187214848.

The previous prime is 6561644483. The next prime is 6561644569. The reversal of 6561644556 is 6554461656.

It is a tau number, because it is divible by the number of its divisors (12).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 273401845 + ... + 273401868.

Almost surely, 2^6561644556 is an apocalyptic number.

It is an amenable number.

6561644556 is an abundant number, since it is smaller than the sum of its proper divisors (8748859436).

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

6561644556 is a wasteful number, since it uses less digits than its factorization.

6561644556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546803720 (or 546803718 counting only the distinct ones).

The product of its digits is 2592000, while the sum is 48.

The square root of 6561644556 is about 81003.9786430272. The cubic root of 6561644556 is about 1872.1367432893.

The spelling of 6561644556 in words is "six billion, five hundred sixty-one million, six hundred forty-four thousand, five hundred fifty-six".