640065 has 16 divisors (see below), whose sum is σ = 1040256. Its totient is φ = 336000.

The previous prime is 640061. The next prime is 640069. The reversal of 640065 is 560046.

640065 = 180² + 181² + ... + 197².

It is an interprime number because it is at equal distance from previous prime (640061) and next prime (640069).

It is not a de Polignac number, because 640065 - 2² = 640061 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (640061) 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 15 ways as a sum of consecutive naturals, for example, 765 + ... + 1365.

It is an arithmetic number, because the mean of its divisors is an integer number (65016).

2⁶⁴⁰⁰⁶⁵ is an apocalyptic number.

It is an amenable number.

640065 is a deficient number, since it is larger than the sum of its proper divisors (400191).

640065 is a wasteful number, since it uses less digits than its factorization.

640065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 680.

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

The square root of 640065 is about 800.0406239686. The cubic root of 640065 is about 86.1803049662.

The spelling of 640065 in words is "six hundred forty thousand, sixty-five".