81819 has 6 divisors (see below), whose sum is σ = 118196. Its totient is φ = 54540.

The previous prime is 81817. The next prime is 81839. The reversal of 81819 is 91818.

It is not a de Polignac number, because 81819 - 2¹ = 81817 is a prime.

It is a super-2 number, since 2×81819² = 13388697522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81792 and 81801.

It is not an unprimeable number, because it can be changed into a prime (81817) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4537 + ... + 4554.

2⁸¹⁸¹⁹ is an apocalyptic number.

81819 is a deficient number, since it is larger than the sum of its proper divisors (36377).

81819 is a wasteful number, since it uses less digits than its factorization.

81819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9097 (or 9094 counting only the distinct ones).

The product of its digits is 576, while the sum is 27.

The square root of 81819 is about 286.0402069640. The cubic root of 81819 is about 43.4128258156.

Subtracting 81819 from its reverse (91818), we obtain a palindrome (9999).

It can be divided in two parts, 81 and 819, that added together give a square (900 = 30²).

The spelling of 81819 in words is "eighty-one thousand, eight hundred nineteen".