261865 has 8 divisors (see below), whose sum is σ = 318528. Its totient is φ = 206640.

The previous prime is 261847. The next prime is 261881. The reversal of 261865 is 568162.

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

It is not a de Polignac number, because 261865 - 2⁹ = 261353 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 100 + ... + 730.

It is an arithmetic number, because the mean of its divisors is an integer number (39816).

2²⁶¹⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

261865 is a deficient number, since it is larger than the sum of its proper divisors (56663).

261865 is an equidigital number, since it uses as much as digits as its factorization.

261865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 719.

The product of its digits is 2880, while the sum is 28.

The square root of 261865 is about 511.7274665288. The cubic root of 261865 is about 63.9772868621.

It can be divided in two parts, 26 and 1865, that added together give a triangular number (1891 = T₆₁).

The spelling of 261865 in words is "two hundred sixty-one thousand, eight hundred sixty-five".