257816861 has 2 divisors, whose sum is σ = 257816862. Its totient is φ = 257816860.

The previous prime is 257816813. The next prime is 257816879. The reversal of 257816861 is 168618752.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 255840025 + 1976836 = 15995^2 + 1406^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-257816861 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (257816161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128908430 + 128908431.

It is an arithmetic number, because the mean of its divisors is an integer number (128908431).

Almost surely, 2^257816861 is an apocalyptic number.

It is an amenable number.

257816861 is a deficient number, since it is larger than the sum of its proper divisors (1).

257816861 is an equidigital number, since it uses as much as digits as its factorization.

257816861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 161280, while the sum is 44.

The square root of 257816861 is about 16056.6765241130. The cubic root of 257816861 is about 636.4590098186.

The spelling of 257816861 in words is "two hundred fifty-seven million, eight hundred sixteen thousand, eight hundred sixty-one".