18666181 has 4 divisors (see below), whose sum is σ = 18774252. Its totient is φ = 18558112.

The previous prime is 18666163. The next prime is 18666203. The reversal of 18666181 is 18166681.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18166681 = 13 ⋅1397437.

It can be written as a sum of positive squares in 2 ways, for example, as 13068225 + 5597956 = 3615^2 + 2366^2 .

It is a cyclic number.

It is not a de Polignac number, because 18666181 - 2¹⁵ = 18633413 is a prime.

It is a super-2 number, since 2×18666181² = 696852626249522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18666181.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18666121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 53776 + ... + 54121.

It is an arithmetic number, because the mean of its divisors is an integer number (4693563).

Almost surely, 2^18666181 is an apocalyptic number.

It is an amenable number.

18666181 is a deficient number, since it is larger than the sum of its proper divisors (108071).

18666181 is a wasteful number, since it uses less digits than its factorization.

18666181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108070.

The product of its digits is 13824, while the sum is 37.

The square root of 18666181 is about 4320.4375935778. The cubic root of 18666181 is about 265.2681799167.

Subtracting from 18666181 its reverse (18166681), we obtain a triangular number (499500 = T₉₉₉).

The spelling of 18666181 in words is "eighteen million, six hundred sixty-six thousand, one hundred eighty-one".