256121 has 2 divisors, whose sum is σ = 256122. Its totient is φ = 256120.

The previous prime is 256117. The next prime is 256129. The reversal of 256121 is 121652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 211600 + 44521 = 460^2 + 211^2 .

It is a cyclic number.

It is not a de Polignac number, because 256121 - 2² = 256117 is a prime.

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

It is equal to p₂₂₅₃₅ and since 256121 and 22535 have the same sum of digits, it is a Honaker prime.

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 256121.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 256121.

It is not a weakly prime, because it can be changed into another prime (256129) 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 as a sum of consecutive naturals, namely, 128060 + 128061.

It is an arithmetic number, because the mean of its divisors is an integer number (128061).

2²⁵⁶¹²¹ is an apocalyptic number.

It is an amenable number.

256121 is a deficient number, since it is larger than the sum of its proper divisors (1).

256121 is an equidigital number, since it uses as much as digits as its factorization.

256121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 120, while the sum is 17.

The square root of 256121 is about 506.0839851250. The cubic root of 256121 is about 63.5060444367.

Adding to 256121 its reverse (121652), we get a palindrome (377773).

It can be divided in two parts, 256 and 121, that multiplied together give a square (30976 = 176²).

The spelling of 256121 in words is "two hundred fifty-six thousand, one hundred twenty-one".