6561516666564 has 18 divisors (see below), whose sum is σ = 16586056018350. Its totient is φ = 2187172222176.

The previous prime is 6561516666563. The next prime is 6561516666577. The reversal of 6561516666564 is 4656666151656.

It can be written as a sum of positive squares in only one way, i.e., 6468273158400 + 93243508164 = 2543280^2 + 305358^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Smith number, since the sum of its digits (63) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (6561516666563) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 91132175889 + ... + 91132175960.

It is an arithmetic number, because the mean of its divisors is an integer number (921447556575).

Almost surely, 2^{6561516666564} is an apocalyptic number.

It is an amenable number.

6561516666564 is an abundant number, since it is smaller than the sum of its proper divisors (10024539351786).

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

6561516666564 is a wasteful number, since it uses less digits than its factorization.

6561516666564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 182264351859 (or 182264351854 counting only the distinct ones).

The product of its digits is 139968000, while the sum is 63.

The spelling of 6561516666564 in words is "six trillion, five hundred sixty-one billion, five hundred sixteen million, six hundred sixty-six thousand, five hundred sixty-four".