640664066 has 32 divisors (see below), whose sum is σ = 1110291840. Its totient is φ = 271584000.

The previous prime is 640664051. The next prime is 640664069. The reversal of 640664066 is 660466046.

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (640664069) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 779936 + ... + 780756.

It is an arithmetic number, because the mean of its divisors is an integer number (34696620).

Almost surely, 2^640664066 is an apocalyptic number.

640664066 is a deficient number, since it is larger than the sum of its proper divisors (469627774).

640664066 is a wasteful number, since it uses less digits than its factorization.

640664066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1370.

The product of its (nonzero) digits is 124416, while the sum is 38.

The square root of 640664066 is about 25311.3426352693. The cubic root of 640664066 is about 862.0718327385.

The spelling of 640664066 in words is "six hundred forty million, six hundred sixty-four thousand, sixty-six".