81281 has 2 divisors, whose sum is σ = 81282.
Its totient is φ = 81280.
The previous prime is 81239. The next prime is 81283. The reversal of 81281 is 18218.
Adding to 81281 its reverse (18218), we get a palindrome (99499).
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 80656 + 625 = 284^2 + 25^2
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-81281 is a prime.
It is a super-2 number, since 2×812812 = 13213201922, which contains 22 as substring.
It is a Sophie Germain prime.
Together with 81283, it forms a pair of twin primes.
It is a Chen prime.
It is a Curzon number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 81281.
It is not a weakly prime, because it can be changed into another prime (81283) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40640 + 40641.
It is an arithmetic number, because the mean of its divisors is an integer number (40641).
281281 is an apocalyptic number.
81281 is the 128-th centered decagonal number.
It is an amenable number.
81281 is a deficient number, since it is larger than the sum of its proper divisors (1).
81281 is an equidigital number, since it uses as much as digits as its factorization.
81281 is an evil number, because the sum of its binary digits is even.
The product of its digits is 128, while the sum is 20.
The square root of 81281 is about 285.0982286862.
The cubic root of 81281 is about 43.3174629589.
The spelling of 81281 in words is "eighty-one thousand, two hundred eighty-one".