256560640 has 160 divisors (see below), whose sum is σ = 714954240. Its totient is φ = 86482944.

The previous prime is 256560631. The next prime is 256560643. The reversal of 256560640 is 46065652.

It is a tau number, because it is divible by the number of its divisors (160).

It is a junction number, because it is equal to n+sod(n) for n = 256560596 and 256560605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256560643) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1845691 + ... + 1845829.

It is an arithmetic number, because the mean of its divisors is an integer number (4468464).

Almost surely, 2^256560640 is an apocalyptic number.

256560640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 256560640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (357477120).

256560640 is an abundant number, since it is smaller than the sum of its proper divisors (458393600).

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

256560640 is a wasteful number, since it uses less digits than its factorization.

256560640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 272 (or 256 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 34.

The square root of 256560640 is about 16017.5104182891. The cubic root of 256560640 is about 635.4236039351.

The spelling of 256560640 in words is "two hundred fifty-six million, five hundred sixty thousand, six hundred forty".