261181 has 4 divisors (see below), whose sum is σ = 263200. Its totient is φ = 259164.

The previous prime is 261169. The next prime is 261223. The reversal of 261181 is 181162.

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 a de Polignac number, because none of the positive numbers 2^k-261181 is a prime.

It is a super-2 number, since 2×261181² = 136431029522, which contains 22 as substring.

It is a Duffinian number.

261181 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 801 + ... + 1078.

It is an arithmetic number, because the mean of its divisors is an integer number (65800).

2²⁶¹¹⁸¹ is an apocalyptic number.

It is an amenable number.

261181 is a deficient number, since it is larger than the sum of its proper divisors (2019).

261181 is a wasteful number, since it uses less digits than its factorization.

261181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2018.

The product of its digits is 96, while the sum is 19.

The square root of 261181 is about 511.0587050428. The cubic root of 261181 is about 63.9215346986.

Subtracting from 261181 its sum of digits (19), we obtain a palindrome (261162).

The spelling of 261181 in words is "two hundred sixty-one thousand, one hundred eighty-one".