639955944 has 64 divisors (see below), whose sum is σ = 1802736000. Its totient is φ = 210309120.

The previous prime is 639955919. The next prime is 639955961. The reversal of 639955944 is 449559936.

639955944 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×639955944² = 819087220521862272, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5529 + ... + 36200.

It is an arithmetic number, because the mean of its divisors is an integer number (28167750).

Almost surely, 2^639955944 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 639955944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (901368000).

639955944 is an abundant number, since it is smaller than the sum of its proper divisors (1162780056).

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

639955944 is a wasteful number, since it uses less digits than its factorization.

639955944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41815 (or 41805 counting only the distinct ones).

The product of its digits is 5248800, while the sum is 54.

The square root of 639955944 is about 25297.3505332080. The cubic root of 639955944 is about 861.7541014393.

The spelling of 639955944 in words is "six hundred thirty-nine million, nine hundred fifty-five thousand, nine hundred forty-four".