256606681 has 4 divisors (see below), whose sum is σ = 259098112. Its totient is φ = 254115252.

The previous prime is 256606673. The next prime is 256606697. The reversal of 256606681 is 186606652.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 256606681 - 2³ = 256606673 is a prime.

It is a super-2 number, since 2×256606681² = 131693977467671522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256606661) 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, 1245561 + ... + 1245766.

It is an arithmetic number, because the mean of its divisors is an integer number (64774528).

Almost surely, 2^256606681 is an apocalyptic number.

It is an amenable number.

256606681 is a deficient number, since it is larger than the sum of its proper divisors (2491431).

256606681 is a wasteful number, since it uses less digits than its factorization.

256606681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2491430.

The product of its (nonzero) digits is 103680, while the sum is 40.

The square root of 256606681 is about 16018.9475621840. The cubic root of 256606681 is about 635.4616115686.

The spelling of 256606681 in words is "two hundred fifty-six million, six hundred six thousand, six hundred eighty-one".