256191517 has 2 divisors, whose sum is σ = 256191518. Its totient is φ = 256191516.

The previous prime is 256191499. The next prime is 256191569. The reversal of 256191517 is 715191652.

256191517 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 226532601 + 29658916 = 15051^2 + 5446^2 .

It is a cyclic number.

It is not a de Polignac number, because 256191517 - 2¹⁹ = 255667229 is a prime.

It is a super-3 number, since 3×256191517³ (a number of 26 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256191587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128095758 + 128095759.

It is an arithmetic number, because the mean of its divisors is an integer number (128095759).

Almost surely, 2^256191517 is an apocalyptic number.

It is an amenable number.

256191517 is a deficient number, since it is larger than the sum of its proper divisors (1).

256191517 is an equidigital number, since it uses as much as digits as its factorization.

256191517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18900, while the sum is 37.

The square root of 256191517 is about 16005.9837873215. The cubic root of 256191517 is about 635.1187220927.

The spelling of 256191517 in words is "two hundred fifty-six million, one hundred ninety-one thousand, five hundred seventeen".