66561016566 has 192 divisors, whose sum is σ = 156967953408. Its totient is φ = 18759840000.

The previous prime is 66561016547. The next prime is 66561016591.

66561016566 is nontrivially palindromic in base 10.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 102876055 + ... + 102876701.

It is an arithmetic number, because the mean of its divisors is an integer number (817541424).

Almost surely, 2^66561016566 is an apocalyptic number.

66561016566 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 66561016566, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (78483976704).

66561016566 is an abundant number, since it is smaller than the sum of its proper divisors (90406936842).

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

66561016566 is a wasteful number, since it uses less digits than its factorization.

66561016566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 859 (or 848 counting only the distinct ones).

The product of its (nonzero) digits is 1166400, while the sum is 48.

The spelling of 66561016566 in words is "sixty-six billion, five hundred sixty-one million, sixteen thousand, five hundred sixty-six".