256021 has 2 divisors, whose sum is σ = 256022. Its totient is φ = 256020.

The previous prime is 256019. The next prime is 256031. The reversal of 256021 is 120652.

It is a happy number.

256021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 239121 + 16900 = 489^2 + 130^2 .

It is a cyclic number.

It is not a de Polignac number, because 256021 - 2¹ = 256019 is a prime.

Together with 256019, it forms a pair of twin primes.

It is a zygodrome in base 4.

It is a junction number, because it is equal to n+sod(n) for n = 255986 and 256004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128010 + 128011.

It is an arithmetic number, because the mean of its divisors is an integer number (128011).

2²⁵⁶⁰²¹ is an apocalyptic number.

It is an amenable number.

256021 is a deficient number, since it is larger than the sum of its proper divisors (1).

256021 is an equidigital number, since it uses as much as digits as its factorization.

256021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 256021 is about 505.9851776485. The cubic root of 256021 is about 63.4977782512.

Adding to 256021 its reverse (120652), we get a palindrome (376673).

The spelling of 256021 in words is "two hundred fifty-six thousand, twenty-one".