181997609 has 2 divisors, whose sum is σ = 181997610. Its totient is φ = 181997608.

The previous prime is 181997581. The next prime is 181997611. The reversal of 181997609 is 906799181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 143520400 + 38477209 = 11980^2 + 6203^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-181997609 is a prime.

Together with 181997611, 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 (181997209) 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, 90998804 + 90998805.

It is an arithmetic number, because the mean of its divisors is an integer number (90998805).

Almost surely, 2^181997609 is an apocalyptic number.

It is an amenable number.

181997609 is a deficient number, since it is larger than the sum of its proper divisors (1).

181997609 is an equidigital number, since it uses as much as digits as its factorization.

181997609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 244944, while the sum is 50.

The square root of 181997609 is about 13490.6489465852. The cubic root of 181997609 is about 566.7026291287.

The spelling of 181997609 in words is "one hundred eighty-one million, nine hundred ninety-seven thousand, six hundred nine".