257921 has 2 divisors, whose sum is σ = 257922. Its totient is φ = 257920.

The previous prime is 257903. The next prime is 257947. The reversal of 257921 is 129752.

It is an a-pointer prime, because the next prime (257947) can be obtained adding 257921 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 250000 + 7921 = 500^2 + 89^2 .

It is a cyclic number.

It is not a de Polignac number, because 257921 - 2⁶ = 257857 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (257981) 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, 128960 + 128961.

It is an arithmetic number, because the mean of its divisors is an integer number (128961).

2²⁵⁷⁹²¹ is an apocalyptic number.

It is an amenable number.

257921 is a deficient number, since it is larger than the sum of its proper divisors (1).

257921 is an equidigital number, since it uses as much as digits as its factorization.

257921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1260, while the sum is 26.

The square root of 257921 is about 507.8592324651. The cubic root of 257921 is about 63.6544692452.

It can be divided in two parts, 25 and 7921, that multiplied together give a square (198025 = 445²).

The spelling of 257921 in words is "two hundred fifty-seven thousand, nine hundred twenty-one".