256605 has 8 divisors (see below), whose sum is σ = 410592. Its totient is φ = 136848.

The previous prime is 256603. The next prime is 256609. The reversal of 256605 is 506652.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 256605 - 2¹ = 256603 is a prime.

It is a super-2 number, since 2×256605² = 131692252050, which contains 22 as substring.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256603) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8539 + ... + 8568.

It is an arithmetic number, because the mean of its divisors is an integer number (51324).

2²⁵⁶⁶⁰⁵ is an apocalyptic number.

It is an amenable number.

256605 is a deficient number, since it is larger than the sum of its proper divisors (153987).

256605 is a wasteful number, since it uses less digits than its factorization.

256605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17115.

The product of its (nonzero) digits is 1800, while the sum is 24.

The square root of 256605 is about 506.5619409312. The cubic root of 256605 is about 63.5460223954.

Subtracting 256605 from its reverse (506652), we obtain a cube (250047 = 63³).

It can be divided in two parts, 256 and 605, that added together give a triangular number (861 = T₄₁).

The spelling of 256605 in words is "two hundred fifty-six thousand, six hundred five".