640834 has 4 divisors (see below), whose sum is σ = 961254. Its totient is φ = 320416.

The previous prime is 640793. The next prime is 640837. The reversal of 640834 is 438046.

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

It can be written as a sum of positive squares in only one way, i.e., 635209 + 5625 = 797^2 + 75^2 .

It is a junction number, because it is equal to n+sod(n) for n = 640799 and 640808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160207 + ... + 160210.

2⁶⁴⁰⁸³⁴ is an apocalyptic number.

640834 is a deficient number, since it is larger than the sum of its proper divisors (320420).

640834 is a wasteful number, since it uses less digits than its factorization.

640834 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320419.

The product of its (nonzero) digits is 2304, while the sum is 25.

The square root of 640834 is about 800.5210802971. The cubic root of 640834 is about 86.2148046557.

The spelling of 640834 in words is "six hundred forty thousand, eight hundred thirty-four".