161940209 has 2 divisors, whose sum is σ = 161940210. Its totient is φ = 161940208.

The previous prime is 161940199. The next prime is 161940223. The reversal of 161940209 is 902049161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 145130209 + 16810000 = 12047^2 + 4100^2 .

It is a cyclic number.

It is not a de Polignac number, because 161940209 - 2¹² = 161936113 is a prime.

It is not a weakly prime, because it can be changed into another prime (161940109) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80970104 + 80970105.

It is an arithmetic number, because the mean of its divisors is an integer number (80970105).

Almost surely, 2^161940209 is an apocalyptic number.

It is an amenable number.

161940209 is a deficient number, since it is larger than the sum of its proper divisors (1).

161940209 is an equidigital number, since it uses as much as digits as its factorization.

161940209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 161940209 is about 12725.5730322842. The cubic root of 161940209 is about 545.0691032653.

The spelling of 161940209 in words is "one hundred sixty-one million, nine hundred forty thousand, two hundred nine".