640795 has 4 divisors (see below), whose sum is σ = 768960. Its totient is φ = 512632.

The previous prime is 640793. The next prime is 640837. The reversal of 640795 is 597046.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 640795 - 2¹ = 640793 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (640793) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 64075 + ... + 64084.

It is an arithmetic number, because the mean of its divisors is an integer number (192240).

2⁶⁴⁰⁷⁹⁵ is an apocalyptic number.

640795 is a deficient number, since it is larger than the sum of its proper divisors (128165).

640795 is a wasteful number, since it uses less digits than its factorization.

640795 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128164.

The product of its (nonzero) digits is 7560, while the sum is 31.

The square root of 640795 is about 800.4967207928. The cubic root of 640795 is about 86.2130556611.

The spelling of 640795 in words is "six hundred forty thousand, seven hundred ninety-five".