640838 has 8 divisors (see below), whose sum is σ = 1048680. Its totient is φ = 291280.

The previous prime is 640837. The next prime is 640847. The reversal of 640838 is 838046.

640838 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 640838.

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 in 3 ways as a sum of consecutive naturals, for example, 14543 + ... + 14586.

It is an arithmetic number, because the mean of its divisors is an integer number (131085).

2⁶⁴⁰⁸³⁸ is an apocalyptic number.

640838 is a deficient number, since it is larger than the sum of its proper divisors (407842).

640838 is a wasteful number, since it uses less digits than its factorization.

640838 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29142.

The product of its (nonzero) digits is 4608, while the sum is 29.

The square root of 640838 is about 800.5235786659. The cubic root of 640838 is about 86.2149840357.

It can be divided in two parts, 6408 and 38, that added together give a palindrome (6446).

The spelling of 640838 in words is "six hundred forty thousand, eight hundred thirty-eight".