666747666 has 64 divisors (see below), whose sum is σ = 1599575040. Its totient is φ = 204647040.

The previous prime is 666747647. The next prime is 666747691.

666747666 is nontrivially palindromic in base 10.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 364831 + ... + 366653.

It is an arithmetic number, because the mean of its divisors is an integer number (24993360).

Almost surely, 2^666747666 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 666747666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (799787520).

666747666 is an abundant number, since it is smaller than the sum of its proper divisors (932827374).

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

666747666 is a wasteful number, since it uses less digits than its factorization.

666747666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2368 (or 2362 counting only the distinct ones).

The product of its digits is 9144576, while the sum is 54.

The square root of 666747666 is about 25821.4574724201. The cubic root of 666747666 is about 873.6158430212.

The spelling of 666747666 in words is "six hundred sixty-six million, seven hundred forty-seven thousand, six hundred sixty-six".