640536 has 32 divisors (see below), whose sum is σ = 1725360. Its totient is φ = 196992.

The previous prime is 640531. The next prime is 640579. The reversal of 640536 is 635046.

It is a Harshad number since it is a multiple of its sum of digits (24).

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 in 7 ways as a sum of consecutive naturals, for example, 715 + ... + 1338.

2⁶⁴⁰⁵³⁶ is an apocalyptic number.

It is an amenable number.

640536 is an abundant number, since it is smaller than the sum of its proper divisors (1084824).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640536 is a wasteful number, since it uses less digits than its factorization.

640536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2075 (or 2071 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 24.

The square root of 640536 is about 800.3349298887. The cubic root of 640536 is about 86.2014387423.

It can be divided in two parts, 6405 and 36, that added together give a triangular number (6441 = T₁₁₃).

The spelling of 640536 in words is "six hundred forty thousand, five hundred thirty-six".