256715209 has 2 divisors, whose sum is σ = 256715210. Its totient is φ = 256715208.

The previous prime is 256715191. The next prime is 256715233. The reversal of 256715209 is 902517652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 205635600 + 51079609 = 14340^2 + 7147^2 .

It is a cyclic number.

It is not a de Polignac number, because 256715209 - 2⁹ = 256714697 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (256715299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128357604 + 128357605.

It is an arithmetic number, because the mean of its divisors is an integer number (128357605).

Almost surely, 2^256715209 is an apocalyptic number.

It is an amenable number.

256715209 is a deficient number, since it is larger than the sum of its proper divisors (1).

256715209 is an equidigital number, since it uses as much as digits as its factorization.

256715209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 37800, while the sum is 37.

The square root of 256715209 is about 16022.3346925472. The cubic root of 256715209 is about 635.5511853048.

The spelling of 256715209 in words is "two hundred fifty-six million, seven hundred fifteen thousand, two hundred nine".