66556800865565 has 16 divisors (see below), whose sum is σ = 80835661827648. Its totient is φ = 52600523243136.

The previous prime is 66556800865549. The next prime is 66556800865603. The reversal of 66556800865565 is 56556800865566.

66556800865565 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 66556800865565 - 2⁴ = 66556800865549 is a prime.

It is a Duffinian number.

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 15 ways as a sum of consecutive naturals, for example, 1234289 + ... + 11603321.

It is an arithmetic number, because the mean of its divisors is an integer number (5052228864228).

Almost surely, 2^{66556800865565} is an apocalyptic number.

It is an amenable number.

66556800865565 is a deficient number, since it is larger than the sum of its proper divisors (14278860962083).

66556800865565 is a wasteful number, since it uses less digits than its factorization.

66556800865565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10384588.

The product of its (nonzero) digits is 1555200000, while the sum is 71.

Subtracting from 66556800865565 its reverse (56556800865566), we obtain a palindrome (9999999999999).

The spelling of 66556800865565 in words is "sixty-six trillion, five hundred fifty-six billion, eight hundred million, eight hundred sixty-five thousand, five hundred sixty-five".