640028 has 12 divisors (see below), whose sum is σ = 1141560. Its totient is φ = 313872.

The previous prime is 640027. The next prime is 640039. The reversal of 640028 is 820046.

It is a nialpdrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 639991 and 640009.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640027) 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, 1298 + ... + 1721.

It is an arithmetic number, because the mean of its divisors is an integer number (95130).

2⁶⁴⁰⁰²⁸ is an apocalyptic number.

It is an amenable number.

640028 is a deficient number, since it is larger than the sum of its proper divisors (501532).

640028 is a wasteful number, since it uses less digits than its factorization.

640028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3076 (or 3074 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 640028 is about 800.0174998086. The cubic root of 640028 is about 86.1786443365.

The spelling of 640028 in words is "six hundred forty thousand, twenty-eight".