256908691 has 4 divisors (see below), whose sum is σ = 276670912. Its totient is φ = 237146472.

The previous prime is 256908661. The next prime is 256908713. The reversal of 256908691 is 196809652.

256908691 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 256908691 - 2¹³ = 256900499 is a prime.

It is a super-2 number, since 2×256908691² = 132004151022666962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256908661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9881091 + ... + 9881116.

It is an arithmetic number, because the mean of its divisors is an integer number (69167728).

Almost surely, 2^256908691 is an apocalyptic number.

256908691 is a deficient number, since it is larger than the sum of its proper divisors (19762221).

256908691 is a wasteful number, since it uses less digits than its factorization.

256908691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19762220.

The product of its (nonzero) digits is 233280, while the sum is 46.

The square root of 256908691 is about 16028.3714394195. The cubic root of 256908691 is about 635.7108133415.

The spelling of 256908691 in words is "two hundred fifty-six million, nine hundred eight thousand, six hundred ninety-one".