666778986 has 16 divisors (see below), whose sum is σ = 1481731200. Its totient is φ = 222259644.

The previous prime is 666778979. The next prime is 666779021. The reversal of 666778986 is 689877666.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6173826 + ... + 6173933.

It is an arithmetic number, because the mean of its divisors is an integer number (92608200).

Almost surely, 2^666778986 is an apocalyptic number.

666778986 is an abundant number, since it is smaller than the sum of its proper divisors (814952214).

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

666778986 is a wasteful number, since it uses less digits than its factorization.

666778986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12347770 (or 12347764 counting only the distinct ones).

The product of its digits is 36578304, while the sum is 63.

The square root of 666778986 is about 25822.0639376484. The cubic root of 666778986 is about 873.6295219691.

The spelling of 666778986 in words is "six hundred sixty-six million, seven hundred seventy-eight thousand, nine hundred eighty-six".