66556800865566 has 96 divisors (see below), whose sum is σ = 158572242466560. Its totient is φ = 20008041984000.

The previous prime is 66556800865549. The next prime is 66556800865603.

66556800865566 is a `hidden beast` number, since 6 + 6 + 5 + 5 + 68 + 0 + 0 + 8 + 6 + 556 + 6 = 666.

66556800865566 is nontrivially palindromic in base 10.

66556800865566 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 66556800865494 and 66556800865503.

It is a congruent number.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 20588446 + ... + 23600798.

It is an arithmetic number, because the mean of its divisors is an integer number (1651794192360).

Almost surely, 2^{66556800865566} is an apocalyptic number.

66556800865566 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 66556800865566, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (79286121233280).

66556800865566 is an abundant number, since it is smaller than the sum of its proper divisors (92015441600994).

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

66556800865566 is a wasteful number, since it uses less digits than its factorization.

66556800865566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3013262 (or 3013259 counting only the distinct ones).

The product of its (nonzero) digits is 1866240000, while the sum is 72.

The spelling of 66556800865566 in words is "sixty-six trillion, five hundred fifty-six billion, eight hundred million, eight hundred sixty-five thousand, five hundred sixty-six".