81161 has 4 divisors (see below), whose sum is σ = 81732. Its totient is φ = 80592.

The previous prime is 81157. The next prime is 81163. The reversal of 81161 is 16118.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 16118 = 2 ⋅8059.

It can be written as a sum of positive squares in 2 ways, for example, as 48400 + 32761 = 220^2 + 181^2 .

It is a cyclic number.

It is not a de Polignac number, because 81161 - 2² = 81157 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81163) 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, 131 + ... + 423.

It is an arithmetic number, because the mean of its divisors is an integer number (20433).

2⁸¹¹⁶¹ is an apocalyptic number.

It is an amenable number.

81161 is a deficient number, since it is larger than the sum of its proper divisors (571).

81161 is a wasteful number, since it uses less digits than its factorization.

81161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 570.

The product of its digits is 48, while the sum is 17.

The square root of 81161 is about 284.8876971721. The cubic root of 81161 is about 43.2961350728.

Adding to 81161 its reverse (16118), we get a palindrome (97279).

It can be divided in two parts, 81 and 161, that multiplied together give a triangular number (13041 = T₁₆₁).

The spelling of 81161 in words is "eighty-one thousand, one hundred sixty-one".