261191 has 4 divisors (see below), whose sum is σ = 298512. Its totient is φ = 223872.

The previous prime is 261169. The next prime is 261223. The reversal of 261191 is 191162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 191162 = 2 ⋅95581.

It is a cyclic number.

It is not a de Polignac number, because 261191 - 2⁶ = 261127 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 (261101) 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, 18650 + ... + 18663.

It is an arithmetic number, because the mean of its divisors is an integer number (74628).

2²⁶¹¹⁹¹ is an apocalyptic number.

261191 is a deficient number, since it is larger than the sum of its proper divisors (37321).

261191 is an equidigital number, since it uses as much as digits as its factorization.

261191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37320.

The product of its digits is 108, while the sum is 20.

The square root of 261191 is about 511.0684885610. The cubic root of 261191 is about 63.9223504895.

The spelling of 261191 in words is "two hundred sixty-one thousand, one hundred ninety-one".