261931 has 4 divisors (see below), whose sum is σ = 267552. Its totient is φ = 256312.

The previous prime is 261917. The next prime is 261959. The reversal of 261931 is 139162.

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

It is a cyclic number.

It is not a de Polignac number, because 261931 - 2¹⁷ = 130859 is a prime.

It is a super-2 number, since 2×261931² = 137215697522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261971) 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, 2740 + ... + 2833.

It is an arithmetic number, because the mean of its divisors is an integer number (66888).

261931 is a Friedman number, since it can be written as (9-1)^6-213, using all its digits and the basic arithmetic operations.

2²⁶¹⁹³¹ is an apocalyptic number.

261931 is a deficient number, since it is larger than the sum of its proper divisors (5621).

261931 is an equidigital number, since it uses as much as digits as its factorization.

261931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5620.

The product of its digits is 324, while the sum is 22.

The square root of 261931 is about 511.7919499172. The cubic root of 261931 is about 63.9826613187.

The spelling of 261931 in words is "two hundred sixty-one thousand, nine hundred thirty-one".