256810509 has 6 divisors (see below), whose sum is σ = 370948526. Its totient is φ = 171207000.

The previous prime is 256810501. The next prime is 256810523. The reversal of 256810509 is 905018652.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 149377284 + 107433225 = 12222^2 + 10365^2 .

It is not a de Polignac number, because 256810509 - 2³ = 256810501 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256810501) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 14267242 + ... + 14267259.

Almost surely, 2^256810509 is an apocalyptic number.

It is an amenable number.

256810509 is a deficient number, since it is larger than the sum of its proper divisors (114138017).

256810509 is a wasteful number, since it uses less digits than its factorization.

256810509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28534507 (or 28534504 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The square root of 256810509 is about 16025.3083901683. The cubic root of 256810509 is about 635.6298204778.

The spelling of 256810509 in words is "two hundred fifty-six million, eight hundred ten thousand, five hundred nine".