181666181 has 2 divisors, whose sum is σ = 181666182. Its totient is φ = 181666180.

The previous prime is 181666171. The next prime is 181666187.

181666181 is nontrivially palindromic in base 10.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 178890625 + 2775556 = 13375^2 + 1666^2 .

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 181666181 - 2⁶ = 181666117 is a prime.

It is a super-2 number, since 2×181666181² = 66005202638249522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181666187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90833090 + 90833091.

It is an arithmetic number, because the mean of its divisors is an integer number (90833091).

Almost surely, 2^181666181 is an apocalyptic number.

It is an amenable number.

181666181 is a deficient number, since it is larger than the sum of its proper divisors (1).

181666181 is an equidigital number, since it uses as much as digits as its factorization.

181666181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 38.

The square root of 181666181 is about 13478.3597295813. The cubic root of 181666181 is about 566.3584208605.

The spelling of 181666181 in words is "one hundred eighty-one million, six hundred sixty-six thousand, one hundred eighty-one".