18172218 has 32 divisors (see below), whose sum is σ = 38753856. Its totient is φ = 5660928.

The previous prime is 18172199. The next prime is 18172243. The reversal of 18172218 is 81227181.

It is a happy number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 16080 + ... + 17172.

It is an arithmetic number, because the mean of its divisors is an integer number (1211058).

Almost surely, 2^18172218 is an apocalyptic number.

18172218 is an abundant number, since it is smaller than the sum of its proper divisors (20581638).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18172218 is a wasteful number, since it uses less digits than its factorization.

18172218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1278.

The product of its digits is 1792, while the sum is 30.

The square root of 18172218 is about 4262.8884573725. Note that the first 3 decimals coincide. The cubic root of 18172218 is about 262.9073005767.

Adding to 18172218 its reverse (81227181), we get a palindrome (99399399).

The spelling of 18172218 in words is "eighteen million, one hundred seventy-two thousand, two hundred eighteen".