639955568 has 160 divisors (see below), whose sum is σ = 1571328000. Its totient is φ = 246343680.

The previous prime is 639955529. The next prime is 639955577. The reversal of 639955568 is 865559936.

It is a Smith number, since the sum of its digits (56) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (56).

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 31 ways as a sum of consecutive naturals, for example, 5871098 + ... + 5871206.

It is an arithmetic number, because the mean of its divisors is an integer number (9820800).

Almost surely, 2^639955568 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 639955568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (785664000).

639955568 is an abundant number, since it is smaller than the sum of its proper divisors (931372432).

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

639955568 is a wasteful number, since it uses less digits than its factorization.

639955568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 263 (or 257 counting only the distinct ones).

The product of its digits is 8748000, while the sum is 56.

The square root of 639955568 is about 25297.3431015986. The cubic root of 639955568 is about 861.7539326674.

The spelling of 639955568 in words is "six hundred thirty-nine million, nine hundred fifty-five thousand, five hundred sixty-eight".