256643660 has 96 divisors (see below), whose sum is σ = 692278272. Its totient is φ = 77679360.

The previous prime is 256643627. The next prime is 256643669. The reversal of 256643660 is 66346652.

It is not an unprimeable number, because it can be changed into a prime (256643669) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 38795 + ... + 44925.

It is an arithmetic number, because the mean of its divisors is an integer number (7211232).

Almost surely, 2^256643660 is an apocalyptic number.

256643660 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 256643660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (346139136).

256643660 is an abundant number, since it is smaller than the sum of its proper divisors (435634612).

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

256643660 is a wasteful number, since it uses less digits than its factorization.

256643660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6183 (or 6181 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 38.

The square root of 256643660 is about 16020.1017474921. The cubic root of 256643660 is about 635.4921350740.

The spelling of 256643660 in words is "two hundred fifty-six million, six hundred forty-three thousand, six hundred sixty".