256640240 has 40 divisors (see below), whose sum is σ = 600379728. Its totient is φ = 102021120.

The previous prime is 256640213. The next prime is 256640309. The reversal of 256640240 is 42046652.

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3200 + ... + 22880.

Almost surely, 2^256640240 is an apocalyptic number.

256640240 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 256640240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (300189864).

256640240 is an abundant number, since it is smaller than the sum of its proper divisors (343739488).

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

256640240 is a wasteful number, since it uses less digits than its factorization.

256640240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19857 (or 19851 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 29.

The square root of 256640240 is about 16019.9950062414. The cubic root of 256640240 is about 635.4893122330.

Adding to 256640240 its reverse (42046652), we get a palindrome (298686892).

The spelling of 256640240 in words is "two hundred fifty-six million, six hundred forty thousand, two hundred forty".