640495 has 4 divisors (see below), whose sum is σ = 768600. Its totient is φ = 512392.

The previous prime is 640483. The next prime is 640499. The reversal of 640495 is 594046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 594046 = 2 ⋅297023.

It is a cyclic number.

It is not a de Polignac number, because 640495 - 2⁵ = 640463 is a prime.

640495 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640499) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64045 + ... + 64054.

It is an arithmetic number, because the mean of its divisors is an integer number (192150).

2⁶⁴⁰⁴⁹⁵ is an apocalyptic number.

640495 is a deficient number, since it is larger than the sum of its proper divisors (128105).

640495 is a wasteful number, since it uses less digits than its factorization.

640495 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128104.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 640495 is about 800.3093152026. The cubic root of 640495 is about 86.1995994835.

The spelling of 640495 in words is "six hundred forty thousand, four hundred ninety-five".