181890109 has 2 divisors, whose sum is σ = 181890110. Its totient is φ = 181890108.

The previous prime is 181890091. The next prime is 181890133. The reversal of 181890109 is 901098181.

It is a happy number.

Together with previous prime (181890091) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 172186884 + 9703225 = 13122^2 + 3115^2 .

It is a cyclic number.

It is not a de Polignac number, because 181890109 - 2¹¹ = 181888061 is a 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 (181890139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90945054 + 90945055.

It is an arithmetic number, because the mean of its divisors is an integer number (90945055).

Almost surely, 2^181890109 is an apocalyptic number.

It is an amenable number.

181890109 is a deficient number, since it is larger than the sum of its proper divisors (1).

181890109 is an equidigital number, since it uses as much as digits as its factorization.

181890109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 37.

The square root of 181890109 is about 13486.6641168230. The cubic root of 181890109 is about 566.5910296201.

The spelling of 181890109 in words is "one hundred eighty-one million, eight hundred ninety thousand, one hundred nine".