208136809 has 2 divisors, whose sum is σ = 208136810. Its totient is φ = 208136808.

The previous prime is 208136807. The next prime is 208136843. The reversal of 208136809 is 908631802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 180311184 + 27825625 = 13428^2 + 5275^2 .

It is a cyclic number.

It is not a de Polignac number, because 208136809 - 2¹ = 208136807 is a prime.

Together with 208136807, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (208136807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104068404 + 104068405.

It is an arithmetic number, because the mean of its divisors is an integer number (104068405).

Almost surely, 2^208136809 is an apocalyptic number.

It is an amenable number.

208136809 is a deficient number, since it is larger than the sum of its proper divisors (1).

208136809 is an equidigital number, since it uses as much as digits as its factorization.

208136809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 208136809 is about 14426.9473208992. The cubic root of 208136809 is about 592.6290878154.

The spelling of 208136809 in words is "two hundred eight million, one hundred thirty-six thousand, eight hundred nine".