18215818 has 4 divisors (see below), whose sum is σ = 27323730. Its totient is φ = 9107908.

The previous prime is 18215801. The next prime is 18215843. The reversal of 18215818 is 81851281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 81851281 = 2113 ⋅38737.

It can be written as a sum of positive squares in only one way, i.e., 17363889 + 851929 = 4167^2 + 923^2 .

It is an unprimeable number.

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, 4553953 + ... + 4553956.

Almost surely, 2^18215818 is an apocalyptic number.

18215818 is a deficient number, since it is larger than the sum of its proper divisors (9107912).

18215818 is an equidigital number, since it uses as much as digits as its factorization.

18215818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9107911.

The product of its digits is 5120, while the sum is 34.

The square root of 18215818 is about 4267.9992970946. Note that the first 3 decimals coincide. The cubic root of 18215818 is about 263.1173942318.

The spelling of 18215818 in words is "eighteen million, two hundred fifteen thousand, eight hundred eighteen".