666978879666 has 96 divisors (see below), whose sum is σ = 1499358369600. Its totient is φ = 197589110400.

The previous prime is 666978879653. The next prime is 666978879689.

666978879666 is nontrivially palindromic in base 10.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 7709940 + ... + 7795968.

It is an arithmetic number, because the mean of its divisors is an integer number (15618316350).

Almost surely, 2^666978879666 is an apocalyptic number.

666978879666 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 666978879666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (749679184800).

666978879666 is an abundant number, since it is smaller than the sum of its proper divisors (832379489934).

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

666978879666 is a wasteful number, since it uses less digits than its factorization.

666978879666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86296 (or 86285 counting only the distinct ones).

The product of its digits is 11851370496, while the sum is 84.

The spelling of 666978879666 in words is "six hundred sixty-six billion, nine hundred seventy-eight million, eight hundred seventy-nine thousand, six hundred sixty-six".