639920640 has 160 divisors (see below), whose sum is σ = 2069242560. Its totient is φ = 168689664.

The previous prime is 639920639. The next prime is 639920653. The reversal of 639920640 is 46029936.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (160).

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, 744531 + ... + 745389.

It is an arithmetic number, because the mean of its divisors is an integer number (12932766).

Almost surely, 2^639920640 is an apocalyptic number.

639920640 is a gapful number since it is divisible by the number (60) 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 639920640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1034621280).

639920640 is an abundant number, since it is smaller than the sum of its proper divisors (1429321920).

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

639920640 is an equidigital number, since it uses as much as digits as its factorization.

639920640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 982 (or 966 counting only the distinct ones).

The product of its (nonzero) digits is 69984, while the sum is 39.

The square root of 639920640 is about 25296.6527430014. The cubic root of 639920640 is about 861.7382545535.

The spelling of 639920640 in words is "six hundred thirty-nine million, nine hundred twenty thousand, six hundred forty".