640005 has 8 divisors (see below), whose sum is σ = 1024032. Its totient is φ = 341328.

The previous prime is 639997. The next prime is 640007. The reversal of 640005 is 500046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 640005 - 2³ = 639997 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15), and also a Moran number because the ratio is a prime number: 42667 = 640005 / (6 + 4 + 0 + 0 + 0 + 5).

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640007) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21319 + ... + 21348.

It is an arithmetic number, because the mean of its divisors is an integer number (128004).

2⁶⁴⁰⁰⁰⁵ is an apocalyptic number.

It is an amenable number.

640005 is a deficient number, since it is larger than the sum of its proper divisors (384027).

640005 is a wasteful number, since it uses less digits than its factorization.

640005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42675.

The product of its (nonzero) digits is 120, while the sum is 15.

The square root of 640005 is about 800.0031249939. The cubic root of 640005 is about 86.1776120210.

The spelling of 640005 in words is "six hundred forty thousand, five".