261331 has 8 divisors (see below), whose sum is σ = 307040. Its totient is φ = 217728.

The previous prime is 261329. The next prime is 261337. The reversal of 261331 is 133162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 261331 - 2¹ = 261329 is a prime.

It is a super-2 number, since 2×261331² = 136587783122, which contains 22 as substring.

It is a Duffinian number.

261331 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261337) 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 7 ways as a sum of consecutive naturals, for example, 246 + ... + 763.

It is an arithmetic number, because the mean of its divisors is an integer number (38380).

2²⁶¹³³¹ is an apocalyptic number.

261331 is a deficient number, since it is larger than the sum of its proper divisors (45709).

261331 is a wasteful number, since it uses less digits than its factorization.

261331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1053.

The product of its digits is 108, while the sum is 16.

The square root of 261331 is about 511.2054381557. The cubic root of 261331 is about 63.9337693753.

Adding to 261331 its reverse (133162), we get a palindrome (394493).

It can be divided in two parts, 2613 and 31, that multiplied together give a triangular number (81003 = T₄₀₂).

The spelling of 261331 in words is "two hundred sixty-one thousand, three hundred thirty-one".