640534 has 4 divisors (see below), whose sum is σ = 960804. Its totient is φ = 320266.

The previous prime is 640531. The next prime is 640579. The reversal of 640534 is 435046.

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

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160132 + ... + 160135.

It is an arithmetic number, because the mean of its divisors is an integer number (240201).

2⁶⁴⁰⁵³⁴ is an apocalyptic number.

640534 is a deficient number, since it is larger than the sum of its proper divisors (320270).

640534 is a wasteful number, since it uses less digits than its factorization.

640534 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320269.

The product of its (nonzero) digits is 1440, while the sum is 22.

The square root of 640534 is about 800.3336804109. Note that the first 3 decimals coincide. The cubic root of 640534 is about 86.2013490242.

The spelling of 640534 in words is "six hundred forty thousand, five hundred thirty-four".