640744 has 32 divisors (see below), whose sum is σ = 1328040. Its totient is φ = 288000.

The previous prime is 640741. The next prime is 640771. The reversal of 640744 is 447046.

It is a happy number.

640744 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 438244 + 202500 = 662^2 + 450^2 .

It is not an unprimeable number, because it can be changed into a prime (640741) 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, 6294 + ... + 6394.

2⁶⁴⁰⁷⁴⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (664020).

640744 is an abundant number, since it is smaller than the sum of its proper divisors (687296).

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

640744 is a wasteful number, since it uses less digits than its factorization.

640744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181 (or 177 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 640744 is about 800.4648649379. The cubic root of 640744 is about 86.2107684072.

The spelling of 640744 in words is "six hundred forty thousand, seven hundred forty-four".