81261 has 6 divisors (see below), whose sum is σ = 117390. Its totient is φ = 54168.

The previous prime is 81239. The next prime is 81281. The reversal of 81261 is 16218.

It can be written as a sum of positive squares in only one way, i.e., 81225 + 36 = 285^2 + 6^2 .

It is not a de Polignac number, because 81261 - 2⁶ = 81197 is a prime.

It is a Curzon number.

81261 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81281) 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 5 ways as a sum of consecutive naturals, for example, 4506 + ... + 4523.

It is an arithmetic number, because the mean of its divisors is an integer number (19565).

2⁸¹²⁶¹ is an apocalyptic number.

It is an amenable number.

81261 is a deficient number, since it is larger than the sum of its proper divisors (36129).

81261 is a wasteful number, since it uses less digits than its factorization.

81261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9035 (or 9032 counting only the distinct ones).

The product of its digits is 96, while the sum is 18.

The square root of 81261 is about 285.0631508982. The cubic root of 81261 is about 43.3139097696.

Adding to 81261 its reverse (16218), we get a palindrome (97479).

The spelling of 81261 in words is "eighty-one thousand, two hundred sixty-one".