256505 has 12 divisors (see below), whose sum is σ = 324012. Its totient is φ = 194880.

The previous prime is 256499. The next prime is 256517. The reversal of 256505 is 505652.

It can be written as a sum of positive squares in 6 ways, for example, as 29929 + 226576 = 173^2 + 476^2 .

It is not a de Polignac number, because 256505 - 2⁴ = 256489 is a prime.

It is a hoax number, since the sum of its digits (23) coincides with the sum of the digits of its distinct prime factors.

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

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 256505.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4175 + ... + 4235.

It is an arithmetic number, because the mean of its divisors is an integer number (27001).

2²⁵⁶⁵⁰⁵ is an apocalyptic number.

It is an amenable number.

256505 is a deficient number, since it is larger than the sum of its proper divisors (67507).

256505 is an equidigital number, since it uses as much as digits as its factorization.

256505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124 (or 95 counting only the distinct ones).

The product of its (nonzero) digits is 1500, while the sum is 23.

The square root of 256505 is about 506.4632267006. The cubic root of 256505 is about 63.5377666094.

The spelling of 256505 in words is "two hundred fifty-six thousand, five hundred five".