161616181 has 2 divisors, whose sum is σ = 161616182. Its totient is φ = 161616180.

The previous prime is 161616179. The next prime is 161616199. The reversal of 161616181 is 181616161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 117180625 + 44435556 = 10825^2 + 6666^2 .

It is a cyclic number.

It is not a de Polignac number, because 161616181 - 2¹ = 161616179 is a prime.

It is a super-2 number, since 2×161616181² = 52239579922049522, which contains 22 as substring.

Together with 161616179, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161616151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80808090 + 80808091.

It is an arithmetic number, because the mean of its divisors is an integer number (80808091).

Almost surely, 2^161616181 is an apocalyptic number.

It is an amenable number.

161616181 is a deficient number, since it is larger than the sum of its proper divisors (1).

161616181 is an equidigital number, since it uses as much as digits as its factorization.

161616181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 31.

The square root of 161616181 is about 12712.8352856473. The cubic root of 161616181 is about 544.7053155390.

The spelling of 161616181 in words is "one hundred sixty-one million, six hundred sixteen thousand, one hundred eighty-one".