647665666 has 8 divisors (see below), whose sum is σ = 972002304. Its totient is φ = 323664900.

The previous prime is 647665633. The next prime is 647665693. The reversal of 647665666 is 666566746.

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 79090 + ... + 86893.

It is an arithmetic number, because the mean of its divisors is an integer number (121500288).

Almost surely, 2^647665666 is an apocalyptic number.

647665666 is a deficient number, since it is larger than the sum of its proper divisors (324336638).

647665666 is a wasteful number, since it uses less digits than its factorization.

647665666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167936.

The product of its digits is 6531840, while the sum is 52.

The square root of 647665666 is about 25449.2763354874. The cubic root of 647665666 is about 865.2008915609.

The spelling of 647665666 in words is "six hundred forty-seven million, six hundred sixty-five thousand, six hundred sixty-six".