256666 has 8 divisors (see below), whose sum is σ = 407700. Its totient is φ = 120768.

The previous prime is 256661. The next prime is 256687. The reversal of 256666 is 666652.

It can be written as a sum of positive squares in 2 ways, for example, as 229441 + 27225 = 479^2 + 165^2 .

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

256666 is a modest number, since divided by 666 gives 256 as remainder.

It is a plaindrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (256661) by changing a digit.

256666 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 3 ways as a sum of consecutive naturals, for example, 3741 + ... + 3808.

2²⁵⁶⁶⁶⁶ is an apocalyptic number.

256666 is a deficient number, since it is larger than the sum of its proper divisors (151034).

256666 is a wasteful number, since it uses less digits than its factorization.

256666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7568.

The product of its digits is 12960, while the sum is 31.

The square root of 256666 is about 506.6221471669. The cubic root of 256666 is about 63.5510573717.

The spelling of 256666 in words is "two hundred fifty-six thousand, six hundred sixty-six".