256566 has 16 divisors (see below), whose sum is σ = 522288. Its totient is φ = 84000.

The previous prime is 256561. The next prime is 256567. The reversal of 256566 is 665652.

It is a super-2 number, since 2×256566² = 131652224712, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16 + ... + 716.

It is an arithmetic number, because the mean of its divisors is an integer number (32643).

2²⁵⁶⁵⁶⁶ is an apocalyptic number.

256566 is an abundant number, since it is smaller than the sum of its proper divisors (265722).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

256566 is a wasteful number, since it uses less digits than its factorization.

256566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 767.

The product of its digits is 10800, while the sum is 30.

The square root of 256566 is about 506.5234446696. The cubic root of 256566 is about 63.5428028941.

The spelling of 256566 in words is "two hundred fifty-six thousand, five hundred sixty-six".