256781555 has 16 divisors (see below), whose sum is σ = 314686944. Its totient is φ = 201077760.

The previous prime is 256781537. The next prime is 256781597. The reversal of 256781555 is 555187652.

It is not a de Polignac number, because 256781555 - 2⁸ = 256781299 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 150467 + ... + 152163.

It is an arithmetic number, because the mean of its divisors is an integer number (19667934).

Almost surely, 2^256781555 is an apocalyptic number.

256781555 is a deficient number, since it is larger than the sum of its proper divisors (57905389).

256781555 is a wasteful number, since it uses less digits than its factorization.

256781555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2326.

The product of its digits is 420000, while the sum is 44.

The square root of 256781555 is about 16024.4049811530. The cubic root of 256781555 is about 635.6059316352.

The spelling of 256781555 in words is "two hundred fifty-six million, seven hundred eighty-one thousand, five hundred fifty-five".