640569 has 4 divisors (see below), whose sum is σ = 854096. Its totient is φ = 427044.

The previous prime is 640531. The next prime is 640579. The reversal of 640569 is 965046.

640569 is nontrivially palindromic in base 2.

640569 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 640569 - 2¹² = 636473 is a prime.

It is a super-2 number, since 2×640569² = 820657287522, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

640569 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (640529) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106759 + ... + 106764.

It is an arithmetic number, because the mean of its divisors is an integer number (213524).

2⁶⁴⁰⁵⁶⁹ is an apocalyptic number.

It is an amenable number.

640569 is a deficient number, since it is larger than the sum of its proper divisors (213527).

640569 is a wasteful number, since it uses less digits than its factorization.

640569 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213526.

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

The square root of 640569 is about 800.3555459919. The cubic root of 640569 is about 86.2029190643.

The spelling of 640569 in words is "six hundred forty thousand, five hundred sixty-nine".