640872 has 80 divisors (see below), whose sum is σ = 1916640. Its totient is φ = 199584.

The previous prime is 640859. The next prime is 640873. The reversal of 640872 is 278046.

640872 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (640873) by changing a digit.

640872 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 19 ways as a sum of consecutive naturals, for example, 14883 + ... + 14925.

It is an arithmetic number, because the mean of its divisors is an integer number (23958).

2⁶⁴⁰⁸⁷² 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 640872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (958320).

640872 is an abundant number, since it is smaller than the sum of its proper divisors (1275768).

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

640872 is a wasteful number, since it uses less digits than its factorization.

640872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84 (or 71 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 640872 is about 800.5448144857. The cubic root of 640872 is about 86.2165087360.

The spelling of 640872 in words is "six hundred forty thousand, eight hundred seventy-two".