640566 has 24 divisors (see below), whose sum is σ = 1461720. Its totient is φ = 202176.

The previous prime is 640531. The next prime is 640579. The reversal of 640566 is 665046.

640566 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640566.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 595 + ... + 1278.

It is an arithmetic number, because the mean of its divisors is an integer number (60905).

2⁶⁴⁰⁵⁶⁶ is an apocalyptic number.

640566 is an abundant number, since it is smaller than the sum of its proper divisors (821154).

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

640566 is a wasteful number, since it uses less digits than its factorization.

640566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1900 (or 1897 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 640566 is about 800.3536718227. The cubic root of 640566 is about 86.2027844917.

The spelling of 640566 in words is "six hundred forty thousand, five hundred sixty-six".