81818 has 8 divisors (see below), whose sum is σ = 133920. Its totient is φ = 37180.

The previous prime is 81817. The next prime is 81839.

81818 = 77² + 78² + ... + 88².

81818 is nontrivially palindromic in base 10.

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

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

81818 is a strobogrammatic number because it is the same when read upside-down.

81818 is an undulating number in base 10.

81818 is a modest number, since divided by 1818 gives 8 as remainder.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81817) 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 3 ways as a sum of consecutive naturals, for example, 1838 + ... + 1881.

It is an arithmetic number, because the mean of its divisors is an integer number (16740).

2⁸¹⁸¹⁸ is an apocalyptic number.

81818 is a deficient number, since it is larger than the sum of its proper divisors (52102).

81818 is a wasteful number, since it uses less digits than its factorization.

81818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3732.

The product of its digits is 512, while the sum is 26.

The square root of 81818 is about 286.0384589526. The cubic root of 81818 is about 43.4126489496.

The spelling of 81818 in words is "eighty-one thousand, eight hundred eighteen".