640944 has 30 divisors (see below), whose sum is σ = 1794156. Its totient is φ = 213600.

The previous prime is 640943. The next prime is 640949. The reversal of 640944 is 449046.

640944 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×640944² = 821618422272, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (640943) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2082 + ... + 2369.

2⁶⁴⁰⁹⁴⁴ is an apocalyptic number.

It is an amenable number.

640944 is an abundant number, since it is smaller than the sum of its proper divisors (1153212).

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

640944 is a wasteful number, since it uses less digits than its factorization.

640944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4465 (or 4456 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 640944 is about 800.5897825978. The cubic root of 640944 is about 86.2197373350.

The spelling of 640944 in words is "six hundred forty thousand, nine hundred forty-four".