261731 has 4 divisors (see below), whose sum is σ = 263112. Its totient is φ = 260352.

The previous prime is 261721. The next prime is 261739. The reversal of 261731 is 137162.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 137162 = 2 ⋅68581.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261731 is a prime.

It is a super-2 number, since 2×261731² = 137006232722, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a zygodrome in base 2.

It is not an unprimeable number, because it can be changed into a prime (261739) 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, 350 + ... + 803.

It is an arithmetic number, because the mean of its divisors is an integer number (65778).

2²⁶¹⁷³¹ is an apocalyptic number.

261731 is a deficient number, since it is larger than the sum of its proper divisors (1381).

261731 is a wasteful number, since it uses less digits than its factorization.

261731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1380.

The product of its digits is 252, while the sum is 20.

The square root of 261731 is about 511.5965207075. The cubic root of 261731 is about 63.9663723080.

Adding to 261731 its reverse (137162), we get a palindrome (398893).

The spelling of 261731 in words is "two hundred sixty-one thousand, seven hundred thirty-one".