256561011 has 36 divisors (see below), whose sum is σ = 434480904. Its totient is φ = 145454400.

The previous prime is 256561007. The next prime is 256561013. The reversal of 256561011 is 110165652.

It is a happy number.

256561011 is a `hidden beast` number, since 2 + 5 + 656 + 1 + 0 + 1 + 1 = 666.

It is not a de Polignac number, because 256561011 - 2² = 256561007 is a prime.

It is not an unprimeable number, because it can be changed into a prime (256561013) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 55551 + ... + 59991.

It is an arithmetic number, because the mean of its divisors is an integer number (12068914).

Almost surely, 2^256561011 is an apocalyptic number.

256561011 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

256561011 is a deficient number, since it is larger than the sum of its proper divisors (177919893).

256561011 is a wasteful number, since it uses less digits than its factorization.

256561011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4592 (or 4582 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 27.

The square root of 256561011 is about 16017.5219993606. The cubic root of 256561011 is about 635.4239102202.

The spelling of 256561011 in words is "two hundred fifty-six million, five hundred sixty-one thousand, eleven".