256649521 has 2 divisors, whose sum is σ = 256649522. Its totient is φ = 256649520.

The previous prime is 256649489. The next prime is 256649539. The reversal of 256649521 is 125946652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 239135296 + 17514225 = 15464^2 + 4185^2 .

It is a cyclic number.

It is not a de Polignac number, because 256649521 - 2⁵ = 256649489 is a prime.

It is not a weakly prime, because it can be changed into another prime (256649581) 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, 128324760 + 128324761.

It is an arithmetic number, because the mean of its divisors is an integer number (128324761).

Almost surely, 2^256649521 is an apocalyptic number.

It is an amenable number.

256649521 is a deficient number, since it is larger than the sum of its proper divisors (1).

256649521 is an equidigital number, since it uses as much as digits as its factorization.

256649521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 129600, while the sum is 40.

The square root of 256649521 is about 16020.2846728764. The cubic root of 256649521 is about 635.4969726389.

The spelling of 256649521 in words is "two hundred fifty-six million, six hundred forty-nine thousand, five hundred twenty-one".