257221 has 2 divisors, whose sum is σ = 257222. Its totient is φ = 257220.

The previous prime is 257219. The next prime is 257239. The reversal of 257221 is 122752.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 236196 + 21025 = 486^2 + 145^2 .

It is a cyclic number.

It is not a de Polignac number, because 257221 - 2¹ = 257219 is a prime.

Together with 257219, it forms a pair of twin primes.

257221 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (257281) 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, 128610 + 128611.

It is an arithmetic number, because the mean of its divisors is an integer number (128611).

2²⁵⁷²²¹ is an apocalyptic number.

It is an amenable number.

257221 is a deficient number, since it is larger than the sum of its proper divisors (1).

257221 is an equidigital number, since it uses as much as digits as its factorization.

257221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 280, while the sum is 19.

The square root of 257221 is about 507.1695968806. The cubic root of 257221 is about 63.5968307955.

Adding to 257221 its reverse (122752), we get a palindrome (379973).

The spelling of 257221 in words is "two hundred fifty-seven thousand, two hundred twenty-one".