640605 has 16 divisors (see below), whose sum is σ = 1171584. Its totient is φ = 292800.

The previous prime is 640589. The next prime is 640613. The reversal of 640605 is 506046.

It is not a de Polignac number, because 640605 - 2⁴ = 640589 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

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 640605.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2946 + ... + 3155.

It is an arithmetic number, because the mean of its divisors is an integer number (73224).

2⁶⁴⁰⁶⁰⁵ is an apocalyptic number.

It is an amenable number.

640605 is a deficient number, since it is larger than the sum of its proper divisors (530979).

640605 is a wasteful number, since it uses less digits than its factorization.

640605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6116.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 640605 is about 800.3780356806. The cubic root of 640605 is about 86.2045339031.

The spelling of 640605 in words is "six hundred forty thousand, six hundred five".