18661818 has 64 divisors (see below), whose sum is σ = 46033920. Its totient is φ = 4922112.

The previous prime is 18661807. The next prime is 18661823. The reversal of 18661818 is 81816681.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 41905 + ... + 42347.

It is an arithmetic number, because the mean of its divisors is an integer number (719280).

Almost surely, 2^18661818 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18661818, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23016960).

18661818 is an abundant number, since it is smaller than the sum of its proper divisors (27372102).

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

18661818 is a wasteful number, since it uses less digits than its factorization.

18661818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 531.

The product of its digits is 18432, while the sum is 39.

The square root of 18661818 is about 4319.9326383637. The cubic root of 18661818 is about 265.2475105351.

The spelling of 18661818 in words is "eighteen million, six hundred sixty-one thousand, eight hundred eighteen".