666688916 has 6 divisors (see below), whose sum is σ = 1166705610. Its totient is φ = 333344456.

The previous prime is 666688909. The next prime is 666688921. The reversal of 666688916 is 619886666.

It can be written as a sum of positive squares in only one way, i.e., 421891600 + 244797316 = 20540^2 + 15646^2 .

It is a super-2 number, since 2×666688916² = 888948221434510112, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83336111 + ... + 83336118.

It is an arithmetic number, because the mean of its divisors is an integer number (194450935).

Almost surely, 2^666688916 is an apocalyptic number.

It is an amenable number.

666688916 is a deficient number, since it is larger than the sum of its proper divisors (500016694).

666688916 is a wasteful number, since it uses less digits than its factorization.

666688916 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166672233 (or 166672231 counting only the distinct ones).

The product of its digits is 4478976, while the sum is 56.

The square root of 666688916 is about 25820.3198276086. The cubic root of 666688916 is about 873.5901829197.

The spelling of 666688916 in words is "six hundred sixty-six million, six hundred eighty-eight thousand, nine hundred sixteen".