256981 has 2 divisors, whose sum is σ = 256982. Its totient is φ = 256980.

The previous prime is 256967. The next prime is 257003. The reversal of 256981 is 189652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 194481 + 62500 = 441^2 + 250^2 .

It is a cyclic number.

It is not a de Polignac number, because 256981 - 2⁹ = 256469 is a prime.

It is a super-2 number, since 2×256981² = 132078468722, which contains 22 as substring.

It is a Chen prime.

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

It is a zygodrome in base 4.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256901) by changing a digit.

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 as a sum of consecutive naturals, namely, 128490 + 128491.

It is an arithmetic number, because the mean of its divisors is an integer number (128491).

2²⁵⁶⁹⁸¹ is an apocalyptic number.

It is an amenable number.

256981 is a deficient number, since it is larger than the sum of its proper divisors (1).

256981 is an equidigital number, since it uses as much as digits as its factorization.

256981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 31.

The square root of 256981 is about 506.9329344203. The cubic root of 256981 is about 63.5770449706.

The spelling of 256981 in words is "two hundred fifty-six thousand, nine hundred eighty-one".