261381 has 8 divisors (see below), whose sum is σ = 351424. Its totient is φ = 172800.

The previous prime is 261379. The next prime is 261389. The reversal of 261381 is 183162.

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

It is not a de Polignac number, because 261381 - 2¹ = 261379 is a prime.

It is a super-2 number, since 2×261381² = 136640054322, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261389) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 165 + ... + 741.

It is an arithmetic number, because the mean of its divisors is an integer number (43928).

2²⁶¹³⁸¹ is an apocalyptic number.

It is an amenable number.

261381 is a deficient number, since it is larger than the sum of its proper divisors (90043).

261381 is a wasteful number, since it uses less digits than its factorization.

261381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 731.

The product of its digits is 288, while the sum is 21.

The square root of 261381 is about 511.2543398349. The cubic root of 261381 is about 63.9378465604.

The spelling of 261381 in words is "two hundred sixty-one thousand, three hundred eighty-one".