18666161 has 2 divisors, whose sum is σ = 18666162. Its totient is φ = 18666160.

The previous prime is 18666157. The next prime is 18666163. The reversal of 18666161 is 16166681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15840400 + 2825761 = 3980^2 + 1681^2 .

It is an emirp because it is prime and its reverse (16166681) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 19199981 and 18999191.

It is a cyclic number.

It is not a de Polignac number, because 18666161 - 2² = 18666157 is a prime.

Together with 18666163, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18666163) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9333080 + 9333081.

It is an arithmetic number, because the mean of its divisors is an integer number (9333081).

Almost surely, 2^18666161 is an apocalyptic number.

It is an amenable number.

18666161 is a deficient number, since it is larger than the sum of its proper divisors (1).

18666161 is an equidigital number, since it uses as much as digits as its factorization.

18666161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 35.

The square root of 18666161 is about 4320.4352789968. The cubic root of 18666161 is about 265.2680851755.

The spelling of 18666161 in words is "eighteen million, six hundred sixty-six thousand, one hundred sixty-one".