256657840 has 40 divisors (see below), whose sum is σ = 631834560. Its totient is φ = 96623616.

The previous prime is 256657811. The next prime is 256657879. The reversal of 256657840 is 48756652.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 93000 + ... + 95719.

It is an arithmetic number, because the mean of its divisors is an integer number (15795864).

Almost surely, 2^256657840 is an apocalyptic number.

256657840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

256657840 is an abundant number, since it is smaller than the sum of its proper divisors (375176720).

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

256657840 is a wasteful number, since it uses less digits than its factorization.

256657840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 188749 (or 188743 counting only the distinct ones).

The product of its (nonzero) digits is 403200, while the sum is 43.

The square root of 256657840 is about 16020.5443103535. The cubic root of 256657840 is about 635.5038388666.

It can be divided in two parts, 2566 and 57840, that added together give a palindrome (60406).

The spelling of 256657840 in words is "two hundred fifty-six million, six hundred fifty-seven thousand, eight hundred forty".