256091681 has 8 divisors (see below), whose sum is σ = 258935040. Its totient is φ = 253255392.

The previous prime is 256091659. The next prime is 256091701. The reversal of 256091681 is 186190652.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 256091681 - 2¹⁸ = 255829537 is a prime.

It is a super-2 number, since 2×256091681² = 131165898154811522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256096681) by changing a digit.

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, 105821 + ... + 108213.

It is an arithmetic number, because the mean of its divisors is an integer number (32366880).

Almost surely, 2^256091681 is an apocalyptic number.

It is an amenable number.

256091681 is a deficient number, since it is larger than the sum of its proper divisors (2843359).

256091681 is a wasteful number, since it uses less digits than its factorization.

256091681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3535.

The product of its (nonzero) digits is 25920, while the sum is 38.

The square root of 256091681 is about 16002.8647747833. The cubic root of 256091681 is about 635.0362109675.

The spelling of 256091681 in words is "two hundred fifty-six million, ninety-one thousand, six hundred eighty-one".