257991 has 8 divisors (see below), whose sum is σ = 359040. Its totient is φ = 164472.

The previous prime is 257989. The next prime is 257993. The reversal of 257991 is 199752.

It is an interprime number because it is at equal distance from previous prime (257989) and next prime (257993).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 257991 - 2¹ = 257989 is a prime.

257991 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 257991.

It is not an unprimeable number, because it can be changed into a prime (257993) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1801 + ... + 1938.

It is an arithmetic number, because the mean of its divisors is an integer number (44880).

2²⁵⁷⁹⁹¹ is an apocalyptic number.

257991 is a deficient number, since it is larger than the sum of its proper divisors (101049).

257991 is a wasteful number, since it uses less digits than its factorization.

257991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3765.

The product of its digits is 5670, while the sum is 33.

The square root of 257991 is about 507.9281445244. The cubic root of 257991 is about 63.6602273518.

The spelling of 257991 in words is "two hundred fifty-seven thousand, nine hundred ninety-one".