255661 has 4 divisors (see below), whose sum is σ = 292192. Its totient is φ = 219132.

The previous prime is 255659. The next prime is 255667. The reversal of 255661 is 166552.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 255661 - 2¹ = 255659 is a prime.

It is a Duffinian number.

255661 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (255667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18255 + ... + 18268.

It is an arithmetic number, because the mean of its divisors is an integer number (73048).

2²⁵⁵⁶⁶¹ is an apocalyptic number.

It is an amenable number.

255661 is a deficient number, since it is larger than the sum of its proper divisors (36531).

255661 is an equidigital number, since it uses as much as digits as its factorization.

255661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36530.

The product of its digits is 1800, while the sum is 25.

The square root of 255661 is about 505.6293108592. The cubic root of 255661 is about 63.4680021483.

The spelling of 255661 in words is "two hundred fifty-five thousand, six hundred sixty-one".