257661 has 10 divisors (see below), whose sum is σ = 385022. Its totient is φ = 171720.

The previous prime is 257657. The next prime is 257671. The reversal of 257661 is 166752.

It can be written as a sum of positive squares in only one way, i.e., 164025 + 93636 = 405^2 + 306^2 .

It is not a de Polignac number, because 257661 - 2² = 257657 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a Curzon number.

257661 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 257661.

It is not an unprimeable number, because it can be changed into a prime (257611) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 1510 + ... + 1671.

2²⁵⁷⁶⁶¹ is an apocalyptic number.

It is an amenable number.

257661 is a deficient number, since it is larger than the sum of its proper divisors (127361).

257661 is an equidigital number, since it uses as much as digits as its factorization.

257661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3193 (or 3184 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 257661 is about 507.6031914793. The cubic root of 257661 is about 63.6330728663.

Subtracting from 257661 its reverse (166752), we obtain a palindrome (90909).

The spelling of 257661 in words is "two hundred fifty-seven thousand, six hundred sixty-one".