256561537 has 2 divisors, whose sum is σ = 256561538. Its totient is φ = 256561536.

The previous prime is 256561507. The next prime is 256561561. The reversal of 256561537 is 735165652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 172948801 + 83612736 = 13151^2 + 9144^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256561537 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 256561537.

It is not a weakly prime, because it can be changed into another prime (256561507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128280768 + 128280769.

It is an arithmetic number, because the mean of its divisors is an integer number (128280769).

Almost surely, 2^256561537 is an apocalyptic number.

It is an amenable number.

256561537 is a deficient number, since it is larger than the sum of its proper divisors (1).

256561537 is an equidigital number, since it uses as much as digits as its factorization.

256561537 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 189000, while the sum is 40.

The square root of 256561537 is about 16017.5384188707. The cubic root of 256561537 is about 635.4243444674.

It can be divided in two parts, 2565615 and 37, that added together give a palindrome (2565652).

The spelling of 256561537 in words is "two hundred fifty-six million, five hundred sixty-one thousand, five hundred thirty-seven".