256509 has 12 divisors (see below), whose sum is σ = 404352. Its totient is φ = 155400.

The previous prime is 256499. The next prime is 256517. The reversal of 256509 is 905652.

256509 is a `hidden beast` number, since 2 + 5 + 650 + 9 = 666.

It is not a de Polignac number, because 256509 - 2⁴ = 256493 is a prime.

It is an alternating number because its digits alternate between even and odd.

256509 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 256509.

It is not an unprimeable number, because it can be changed into a prime (256579) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1197 + ... + 1394.

It is an arithmetic number, because the mean of its divisors is an integer number (33696).

2²⁵⁶⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

256509 is a deficient number, since it is larger than the sum of its proper divisors (147843).

256509 is a wasteful number, since it uses less digits than its factorization.

256509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2608 (or 2605 counting only the distinct ones).

The product of its (nonzero) digits is 2700, while the sum is 27.

The square root of 256509 is about 506.4671756393. The cubic root of 256509 is about 63.5380968821.

The spelling of 256509 in words is "two hundred fifty-six thousand, five hundred nine".