261491 has 4 divisors (see below), whose sum is σ = 264000. Its totient is φ = 258984.

The previous prime is 261467. The next prime is 261509. The reversal of 261491 is 194162.

It is a happy number.

261491 is nontrivially palindromic in base 6.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 194162 = 2 ⋅97081.

It is not a de Polignac number, because 261491 - 2⁶ = 261427 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261431) 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, 1091 + ... + 1308.

It is an arithmetic number, because the mean of its divisors is an integer number (66000).

2²⁶¹⁴⁹¹ is an apocalyptic number.

261491 is a deficient number, since it is larger than the sum of its proper divisors (2509).

261491 is a wasteful number, since it uses less digits than its factorization.

261491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2508.

The product of its digits is 432, while the sum is 23.

The square root of 261491 is about 511.3619070678. The cubic root of 261491 is about 63.9468145379.

The spelling of 261491 in words is "two hundred sixty-one thousand, four hundred ninety-one".