18181816 has 8 divisors (see below), whose sum is σ = 34090920. Its totient is φ = 9090904.

The previous prime is 18181783. The next prime is 18181817. The reversal of 18181816 is 61818181.

It is a tau number, because it is divible by the number of its divisors (8).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18181817) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1136356 + ... + 1136371.

It is an arithmetic number, because the mean of its divisors is an integer number (4261365).

Almost surely, 2^18181816 is an apocalyptic number.

It is an amenable number.

18181816 is a deficient number, since it is larger than the sum of its proper divisors (15909104).

18181816 is a wasteful number, since it uses less digits than its factorization.

18181816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2272733 (or 2272729 counting only the distinct ones).

The product of its digits is 3072, while the sum is 34.

The square root of 18181816 is about 4264.0140712713. The cubic root of 18181816 is about 262.9535789148.

Adding to 18181816 its reverse (61818181), we get a palindrome (79999997).

The spelling of 18181816 in words is "eighteen million, one hundred eighty-one thousand, eight hundred sixteen".