640680866 has 16 divisors (see below), whose sum is σ = 1098861504. Its totient is φ = 274439664.

The previous prime is 640680851. The next prime is 640680871. The reversal of 640680866 is 668086046.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20456 + ... + 41228.

It is an arithmetic number, because the mean of its divisors is an integer number (68678844).

Almost surely, 2^640680866 is an apocalyptic number.

640680866 is a deficient number, since it is larger than the sum of its proper divisors (458180638).

640680866 is a wasteful number, since it uses less digits than its factorization.

640680866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22985.

The product of its (nonzero) digits is 331776, while the sum is 44.

The square root of 640680866 is about 25311.6745001195. The cubic root of 640680866 is about 862.0793679825.

The spelling of 640680866 in words is "six hundred forty million, six hundred eighty thousand, eight hundred sixty-six".