639920 has 40 divisors (see below), whose sum is σ = 1569840. Its totient is φ = 241920.

The previous prime is 639911. The next prime is 639937. The reversal of 639920 is 29936.

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

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639920.

It is an unprimeable number.

639920 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1310 + ... + 1730.

It is an arithmetic number, because the mean of its divisors is an integer number (39246).

2⁶³⁹⁹²⁰ 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 639920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (784920).

639920 is an abundant number, since it is smaller than the sum of its proper divisors (929920).

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

639920 is a wasteful number, since it uses less digits than its factorization.

639920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 453 (or 447 counting only the distinct ones).

The product of its (nonzero) digits is 2916, while the sum is 29.

The square root of 639920 is about 799.9499984374. The cubic root of 639920 is about 86.1737967272.

The spelling of 639920 in words is "six hundred thirty-nine thousand, nine hundred twenty".