640532660 has 24 divisors (see below), whose sum is σ = 1363547976. Its totient is φ = 252702720.

The previous prime is 640532623. The next prime is 640532671. The reversal of 640532660 is 66235046.

It can be written as a sum of positive squares in 4 ways, for example, as 128958736 + 511573924 = 11356^2 + 22618^2 .

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 217901 + ... + 220820.

It is an arithmetic number, because the mean of its divisors is an integer number (56814499).

Almost surely, 2^640532660 is an apocalyptic number.

It is an amenable number.

640532660 is an abundant number, since it is smaller than the sum of its proper divisors (723015316).

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

640532660 is a wasteful number, since it uses less digits than its factorization.

640532660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 438803 (or 438801 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 32.

The square root of 640532660 is about 25308.7467093888. The cubic root of 640532660 is about 862.0128891292.

The spelling of 640532660 in words is "six hundred forty million, five hundred thirty-two thousand, six hundred sixty".