257720857 has 2 divisors, whose sum is σ = 257720858. Its totient is φ = 257720856.

The previous prime is 257720851. The next prime is 257720861. The reversal of 257720857 is 758027752.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 243703321 + 14017536 = 15611^2 + 3744^2 .

It is a cyclic number.

It is not a de Polignac number, because 257720857 - 2²⁷ = 123503129 is a prime.

It is not a weakly prime, because it can be changed into another prime (257720851) 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, 128860428 + 128860429.

It is an arithmetic number, because the mean of its divisors is an integer number (128860429).

Almost surely, 2^257720857 is an apocalyptic number.

It is an amenable number.

257720857 is a deficient number, since it is larger than the sum of its proper divisors (1).

257720857 is an equidigital number, since it uses as much as digits as its factorization.

257720857 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 274400, while the sum is 43.

The square root of 257720857 is about 16053.6867105347. The cubic root of 257720857 is about 636.3799999917.

The spelling of 257720857 in words is "two hundred fifty-seven million, seven hundred twenty thousand, eight hundred fifty-seven".