256331661 has 24 divisors (see below), whose sum is σ = 366125760. Its totient is φ = 158969472.

The previous prime is 256331651. The next prime is 256331683. The reversal of 256331661 is 166133652.

It is not a de Polignac number, because 256331661 - 2⁵ = 256331629 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256331611) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 583680 + ... + 584118.

It is an arithmetic number, because the mean of its divisors is an integer number (15255240).

Almost surely, 2^256331661 is an apocalyptic number.

It is an amenable number.

256331661 is a deficient number, since it is larger than the sum of its proper divisors (109794099).

256331661 is a wasteful number, since it uses less digits than its factorization.

256331661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 673 (or 566 counting only the distinct ones).

The product of its digits is 19440, while the sum is 33.

The square root of 256331661 is about 16010.3610515191. The cubic root of 256331661 is about 635.2345102788.

The spelling of 256331661 in words is "two hundred fifty-six million, three hundred thirty-one thousand, six hundred sixty-one".