261565 has 4 divisors (see below), whose sum is σ = 313884. Its totient is φ = 209248.

The previous prime is 261563. The next prime is 261577. The reversal of 261565 is 565162.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 181476 + 80089 = 426^2 + 283^2 .

It is a cyclic number.

It is not a de Polignac number, because 261565 - 2¹ = 261563 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261563) 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, 26152 + ... + 26161.

It is an arithmetic number, because the mean of its divisors is an integer number (78471).

2²⁶¹⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

261565 is a deficient number, since it is larger than the sum of its proper divisors (52319).

261565 is an equidigital number, since it uses as much as digits as its factorization.

261565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52318.

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

The square root of 261565 is about 511.4342577497. The cubic root of 261565 is about 63.9528461259.

The spelling of 261565 in words is "two hundred sixty-one thousand, five hundred sixty-five".