640385856 has 168 divisors, whose sum is σ = 2041269984. Its totient is φ = 190295040.

The previous prime is 640385843. The next prime is 640385891. The reversal of 640385856 is 658583046.

640385856 is a `hidden beast` number, since 64 + 0 + 3 + 8 + 585 + 6 = 666.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 334855 + ... + 336761.

Almost surely, 2^640385856 is an apocalyptic number.

640385856 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640385856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1020634992).

640385856 is an abundant number, since it is smaller than the sum of its proper divisors (1400884128).

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

640385856 is a wasteful number, since it uses less digits than its factorization.

640385856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1989 (or 1976 counting only the distinct ones).

The product of its (nonzero) digits is 691200, while the sum is 45.

The square root of 640385856 is about 25305.8462810474. The cubic root of 640385856 is about 861.9470290427.

The spelling of 640385856 in words is "six hundred forty million, three hundred eighty-five thousand, eight hundred fifty-six".