81818217 has 24 divisors (see below), whose sum is σ = 127600200. Its totient is φ = 50220288.

The previous prime is 81818197. The next prime is 81818227. The reversal of 81818217 is 71281818.

It can be written as a sum of positive squares in 4 ways, for example, as 9585216 + 72233001 = 3096^2 + 8499^2 .

It is not a de Polignac number, because 81818217 - 2¹¹ = 81816169 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81818227) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 65959 + ... + 67187.

It is an arithmetic number, because the mean of its divisors is an integer number (5316675).

Almost surely, 2^81818217 is an apocalyptic number.

It is an amenable number.

81818217 is a deficient number, since it is larger than the sum of its proper divisors (45781983).

81818217 is a wasteful number, since it uses less digits than its factorization.

81818217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1817 (or 1814 counting only the distinct ones).

The product of its digits is 7168, while the sum is 36.

The square root of 81818217 is about 9045.3422820809. The cubic root of 81818217 is about 434.1268732965.

The spelling of 81818217 in words is "eighty-one million, eight hundred eighteen thousand, two hundred seventeen".