640128 has 32 divisors (see below), whose sum is σ = 1701360. Its totient is φ = 213248.

The previous prime is 640127. The next prime is 640139. The reversal of 640128 is 821046.

It is a tau number, because it is divible by the number of its divisors (32).

It is not an unprimeable number, because it can be changed into a prime (640121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 450 + ... + 1217.

2⁶⁴⁰¹²⁸ is an apocalyptic number.

It is an amenable number.

640128 is an abundant number, since it is smaller than the sum of its proper divisors (1061232).

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

640128 is a wasteful number, since it uses less digits than its factorization.

640128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1684 (or 1672 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 640128 is about 800.0799960004. The cubic root of 640128 is about 86.1831323775.

The spelling of 640128 in words is "six hundred forty thousand, one hundred twenty-eight".