256813309 has 2 divisors, whose sum is σ = 256813310. Its totient is φ = 256813308.

The previous prime is 256813307. The next prime is 256813351. The reversal of 256813309 is 903318652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 248945284 + 7868025 = 15778^2 + 2805^2 .

It is a cyclic number.

It is not a de Polignac number, because 256813309 - 2¹ = 256813307 is a prime.

Together with 256813307, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256813303) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128406654 + 128406655.

It is an arithmetic number, because the mean of its divisors is an integer number (128406655).

Almost surely, 2^256813309 is an apocalyptic number.

It is an amenable number.

256813309 is a deficient number, since it is larger than the sum of its proper divisors (1).

256813309 is an equidigital number, since it uses as much as digits as its factorization.

256813309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 38880, while the sum is 37.

The square root of 256813309 is about 16025.3957517435. The cubic root of 256813309 is about 635.6321305560.

The spelling of 256813309 in words is "two hundred fifty-six million, eight hundred thirteen thousand, three hundred nine".