8181 has 10 divisors (see below), whose sum is σ = 12342. Its totient is φ = 5400.

The previous prime is 8179. The next prime is 8191. The reversal of 8181 is 1818.

8181 = 5³ + 6³ + ... + 13³.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 8100 + 81 = 90^2 + 9^2 .

It is not a de Polignac number, because 8181 - 2¹ = 8179 is a prime.

It is a super-2 number, since 2×8181² = 133857522, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

8181 is an undulating number in base 10.

It is a Curzon number.

It is a plaindrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8101) 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 9 ways as a sum of consecutive naturals, for example, 31 + ... + 131.

2⁸¹⁸¹ is an apocalyptic number.

8181 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

8181 is a deficient number, since it is larger than the sum of its proper divisors (4161).

8181 is a wasteful number, since it uses less digits than its factorization.

8181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 113 (or 104 counting only the distinct ones).

The product of its digits is 64, while the sum is 18.

The square root of 8181 is about 90.4488805901. The cubic root of 8181 is about 20.1497098846.

Adding to 8181 its reverse (1818), we get a palindrome (9999).

The spelling of 8181 in words is "eight thousand, one hundred eighty-one".