181997180509 has 2 divisors, whose sum is σ = 181997180510. Its totient is φ = 181997180508.

The previous prime is 181997180479. The next prime is 181997180513. The reversal of 181997180509 is 905081799181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 181985000409 + 12180100 = 426597^2 + 3490^2 .

It is a cyclic number.

It is not a de Polignac number, because 181997180509 - 2⁹ = 181997179997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181997180609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90998590254 + 90998590255.

It is an arithmetic number, because the mean of its divisors is an integer number (90998590255).

Almost surely, 2^181997180509 is an apocalyptic number.

It is an amenable number.

181997180509 is a deficient number, since it is larger than the sum of its proper divisors (1).

181997180509 is an equidigital number, since it uses as much as digits as its factorization.

181997180509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1632960, while the sum is 58.

The spelling of 181997180509 in words is "one hundred eighty-one billion, nine hundred ninety-seven million, one hundred eighty thousand, five hundred nine".