665866641 has 16 divisors (see below), whose sum is σ = 969292800. Its totient is φ = 403239120.

The previous prime is 665866637. The next prime is 665866657. The reversal of 665866641 is 146668566.

It is not a de Polignac number, because 665866641 - 2² = 665866637 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (665866631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38956 + ... + 53378.

It is an arithmetic number, because the mean of its divisors is an integer number (60580800).

Almost surely, 2^665866641 is an apocalyptic number.

It is an amenable number.

665866641 is a deficient number, since it is larger than the sum of its proper divisors (303426159).

665866641 is a wasteful number, since it uses less digits than its factorization.

665866641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15836.

The product of its digits is 1244160, while the sum is 48.

The square root of 665866641 is about 25804.3918936293. The cubic root of 665866641 is about 873.2308814643.

The spelling of 665866641 in words is "six hundred sixty-five million, eight hundred sixty-six thousand, six hundred forty-one".