640940664 has 256 divisors, whose sum is σ = 2129863680. Its totient is φ = 155934720.

The previous prime is 640940653. The next prime is 640940669. The reversal of 640940664 is 466049046.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640940669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2264667 + ... + 2264949.

It is an arithmetic number, because the mean of its divisors is an integer number (8319780).

Almost surely, 2^640940664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640940664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1064931840).

640940664 is an abundant number, since it is smaller than the sum of its proper divisors (1488923016).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640940664 is a wasteful number, since it uses less digits than its factorization.

640940664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 390 (or 386 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 39.

The square root of 640940664 is about 25316.8059596782. The cubic root of 640940664 is about 862.1958774863.

The spelling of 640940664 in words is "six hundred forty million, nine hundred forty thousand, six hundred sixty-four".