261845 has 4 divisors (see below), whose sum is σ = 314220. Its totient is φ = 209472.

The previous prime is 261823. The next prime is 261847. The reversal of 261845 is 548162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 548162 = 2 ⋅274081.

It can be written as a sum of positive squares in 2 ways, for example, as 142129 + 119716 = 377^2 + 346^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261845 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261847) 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, 26180 + ... + 26189.

It is an arithmetic number, because the mean of its divisors is an integer number (78555).

2²⁶¹⁸⁴⁵ is an apocalyptic number.

It is an amenable number.

261845 is a deficient number, since it is larger than the sum of its proper divisors (52375).

261845 is an equidigital number, since it uses as much as digits as its factorization.

261845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52374.

The product of its digits is 1920, while the sum is 26.

The square root of 261845 is about 511.7079245038. The cubic root of 261845 is about 63.9756580606.

The spelling of 261845 in words is "two hundred sixty-one thousand, eight hundred forty-five".