640244 has 12 divisors (see below), whose sum is σ = 1222368. Its totient is φ = 291000.

The previous prime is 640231. The next prime is 640247. The reversal of 640244 is 442046.

640244 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a hoax number, since the sum of its digits (20) coincides with the sum of the digits of its distinct prime factors.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640247) 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, 7232 + ... + 7319.

It is an arithmetic number, because the mean of its divisors is an integer number (101864).

2⁶⁴⁰²⁴⁴ is an apocalyptic number.

It is an amenable number.

640244 is a deficient number, since it is larger than the sum of its proper divisors (582124).

640244 is a wasteful number, since it uses less digits than its factorization.

640244 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14566 (or 14564 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 20.

The square root of 640244 is about 800.1524854676. The cubic root of 640244 is about 86.1883379195.

It can be divided in two parts, 6402 and 44, that added together give a palindrome (6446).

The spelling of 640244 in words is "six hundred forty thousand, two hundred forty-four".