640844 has 12 divisors (see below), whose sum is σ = 1129968. Its totient is φ = 318000.

The previous prime is 640837. The next prime is 640847. The reversal of 640844 is 448046.

640844 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (640847) by changing a digit.

640844 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 3 ways as a sum of consecutive naturals, for example, 74 + ... + 1134.

It is an arithmetic number, because the mean of its divisors is an integer number (94164).

2⁶⁴⁰⁸⁴⁴ is an apocalyptic number.

It is an amenable number.

640844 is a deficient number, since it is larger than the sum of its proper divisors (489124).

640844 is a wasteful number, since it uses less digits than its factorization.

640844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1216 (or 1214 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 26.

The square root of 640844 is about 800.5273262044. The cubic root of 640844 is about 86.2152531044.

The spelling of 640844 in words is "six hundred forty thousand, eight hundred forty-four".