640256 has 36 divisors (see below), whose sum is σ = 1330644. Its totient is φ = 307200.

The previous prime is 640249. The next prime is 640259. The reversal of 640256 is 652046.

It can be written as a sum of positive squares in 2 ways, for example, as 25600 + 614656 = 160^2 + 784^2 .

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640256.

It is not an unprimeable number, because it can be changed into a prime (640259) 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, 10466 + ... + 10526.

2⁶⁴⁰²⁵⁶ 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 640256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (665322).

640256 is an abundant number, since it is smaller than the sum of its proper divisors (690388).

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

640256 is an equidigital number, since it uses as much as digits as its factorization.

640256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118 (or 104 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 640256 is about 800.1599840032. The cubic root of 640256 is about 86.1888763879.

The spelling of 640256 in words is "six hundred forty thousand, two hundred fifty-six".