256474617821 has 2 divisors, whose sum is σ = 256474617822. Its totient is φ = 256474617820.

The previous prime is 256474617809. The next prime is 256474617887. The reversal of 256474617821 is 128716474652.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 249339436921 + 7135180900 = 499339^2 + 84470^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256474617821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256474617221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128237308910 + 128237308911.

It is an arithmetic number, because the mean of its divisors is an integer number (128237308911).

Almost surely, 2^256474617821 is an apocalyptic number.

It is an amenable number.

256474617821 is a deficient number, since it is larger than the sum of its proper divisors (1).

256474617821 is an equidigital number, since it uses as much as digits as its factorization.

256474617821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4515840, while the sum is 53.

The spelling of 256474617821 in words is "two hundred fifty-six billion, four hundred seventy-four million, six hundred seventeen thousand, eight hundred twenty-one".