81205 has 8 divisors (see below), whose sum is σ = 99000. Its totient is φ = 63936.

The previous prime is 81203. The next prime is 81223. The reversal of 81205 is 50218.

81205 = 201² + 202².

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 3364 + 77841 = 58^2 + 279^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 81205 - 2¹ = 81203 is a prime.

It is a plaindrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81203) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 471 + ... + 619.

It is an arithmetic number, because the mean of its divisors is an integer number (12375).

2⁸¹²⁰⁵ is an apocalyptic number.

81205 is the 202-nd centered square number.

It is an amenable number.

81205 is a deficient number, since it is larger than the sum of its proper divisors (17795).

81205 is a wasteful number, since it uses less digits than its factorization.

81205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 263.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 81205 is about 284.9649101205. The cubic root of 81205 is about 43.3039577371.

The spelling of 81205 in words is "eighty-one thousand, two hundred five".