256506661 has 2 divisors, whose sum is σ = 256506662. Its totient is φ = 256506660.

The previous prime is 256506643. The next prime is 256506737. The reversal of 256506661 is 166605652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 246678436 + 9828225 = 15706^2 + 3135^2 .

It is a cyclic number.

It is not a de Polignac number, because 256506661 - 2¹¹ = 256504613 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 256506661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256506611) 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 as a sum of consecutive naturals, namely, 128253330 + 128253331.

It is an arithmetic number, because the mean of its divisors is an integer number (128253331).

Almost surely, 2^256506661 is an apocalyptic number.

It is an amenable number.

256506661 is a deficient number, since it is larger than the sum of its proper divisors (1).

256506661 is an equidigital number, since it uses as much as digits as its factorization.

256506661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64800, while the sum is 37.

The square root of 256506661 is about 16015.8253299666. The cubic root of 256506661 is about 635.3790375557.

The spelling of 256506661 in words is "two hundred fifty-six million, five hundred six thousand, six hundred sixty-one".