261855 has 36 divisors (see below), whose sum is σ = 517608. Its totient is φ = 121440.

The previous prime is 261847. The next prime is 261881. The reversal of 261855 is 558162.

It is not a de Polignac number, because 261855 - 2³ = 261847 is a prime.

It is an Ulam number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 11374 + ... + 11396.

It is an arithmetic number, because the mean of its divisors is an integer number (14378).

261855 is a Friedman number, since it can be written as 55*(61+8)^2, using all its digits and the basic arithmetic operations.

2²⁶¹⁸⁵⁵ is an apocalyptic number.

261855 is a deficient number, since it is larger than the sum of its proper divisors (255753).

261855 is a wasteful number, since it uses less digits than its factorization.

261855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68 (or 42 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 261855 is about 511.7176956096. The cubic root of 261855 is about 63.9764724717.

It can be divided in two parts, 26 and 1855, that added together give a palindrome (1881).

The spelling of 261855 in words is "two hundred sixty-one thousand, eight hundred fifty-five".