640695 has 24 divisors (see below), whose sum is σ = 1129968. Its totient is φ = 309760.

The previous prime is 640691. The next prime is 640727. The reversal of 640695 is 596046.

It is not a de Polignac number, because 640695 - 2² = 640691 is a prime.

640695 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640691) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1639 + ... + 1991.

It is an arithmetic number, because the mean of its divisors is an integer number (47082).

2⁶⁴⁰⁶⁹⁵ is an apocalyptic number.

640695 is a deficient number, since it is larger than the sum of its proper divisors (489273).

640695 is a wasteful number, since it uses less digits than its factorization.

640695 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 383 (or 372 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 640695 is about 800.4342571380. The cubic root of 640695 is about 86.2085707353.

The spelling of 640695 in words is "six hundred forty thousand, six hundred ninety-five".