639760 has 40 divisors (see below), whose sum is σ = 1624896. Its totient is φ = 232320.

The previous prime is 639757. The next prime is 639833. The reversal of 639760 is 67936.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 517 + ... + 1243.

2⁶³⁹⁷⁶⁰ 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 639760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (812448).

639760 is an abundant number, since it is smaller than the sum of its proper divisors (985136).

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

639760 is a wasteful number, since it uses less digits than its factorization.

639760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 751 (or 745 counting only the distinct ones).

The product of its (nonzero) digits is 6804, while the sum is 31.

The square root of 639760 is about 799.8499859349. The cubic root of 639760 is about 86.1666140810.

The spelling of 639760 in words is "six hundred thirty-nine thousand, seven hundred sixty".