640735 has 4 divisors (see below), whose sum is σ = 768888. Its totient is φ = 512584.

The previous prime is 640733. The next prime is 640741. The reversal of 640735 is 537046.

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

It is a cyclic number.

It is not a de Polignac number, because 640735 - 2¹ = 640733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640733) 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, 64069 + ... + 64078.

It is an arithmetic number, because the mean of its divisors is an integer number (192222).

2⁶⁴⁰⁷³⁵ is an apocalyptic number.

640735 is a deficient number, since it is larger than the sum of its proper divisors (128153).

640735 is a wasteful number, since it uses less digits than its factorization.

640735 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128152.

The product of its (nonzero) digits is 2520, while the sum is 25.

The square root of 640735 is about 800.4592431848. The cubic root of 640735 is about 86.2103647616.

The spelling of 640735 in words is "six hundred forty thousand, seven hundred thirty-five".