81843218 has 6 divisors (see below), whose sum is σ = 122784021. Its totient is φ = 40915212.

The previous prime is 81843211. The next prime is 81843239. The reversal of 81843218 is 81234818.

It can be written as a sum of positive squares in 2 ways, for example, as 48121969 + 33721249 = 6937^2 + 5807^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=6397.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81843211) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 9596 + ... + 15992.

Almost surely, 2^81843218 is an apocalyptic number.

81843218 is a deficient number, since it is larger than the sum of its proper divisors (40940803).

81843218 is an frugal number, since it uses more digits than its factorization.

81843218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12796 (or 6399 counting only the distinct ones).

The product of its digits is 12288, while the sum is 35.

The square root of 81843218 is about 9046.7241585007. The cubic root of 81843218 is about 434.1710871690.

Subtracting from 81843218 its reverse (81234818), we obtain a square (608400 = 780²).

The spelling of 81843218 in words is "eighty-one million, eight hundred forty-three thousand, two hundred eighteen".