208609409 has 2 divisors, whose sum is σ = 208609410. Its totient is φ = 208609408.

The previous prime is 208609361. The next prime is 208609411. The reversal of 208609409 is 904906802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 208167184 + 442225 = 14428^2 + 665^2 .

It is a cyclic number.

It is not a de Polignac number, because 208609409 - 2²⁰ = 207560833 is a prime.

Together with 208609411, 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 (208609439) 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, 104304704 + 104304705.

It is an arithmetic number, because the mean of its divisors is an integer number (104304705).

Almost surely, 2^208609409 is an apocalyptic number.

It is an amenable number.

208609409 is a deficient number, since it is larger than the sum of its proper divisors (1).

208609409 is an equidigital number, since it uses as much as digits as its factorization.

208609409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31104, while the sum is 38.

The square root of 208609409 is about 14443.3171051528. The cubic root of 208609409 is about 593.0772942821.

The spelling of 208609409 in words is "two hundred eight million, six hundred nine thousand, four hundred nine".