208688009 has 2 divisors, whose sum is σ = 208688010. Its totient is φ = 208688008.

The previous prime is 208687981. The next prime is 208688047. The reversal of 208688009 is 900886802.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 206353225 + 2334784 = 14365^2 + 1528^2 .

It is a cyclic number.

It is not a de Polignac number, because 208688009 - 2²⁰ = 207639433 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (208688069) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104344004 + 104344005.

It is an arithmetic number, because the mean of its divisors is an integer number (104344005).

Almost surely, 2^208688009 is an apocalyptic number.

It is an amenable number.

208688009 is a deficient number, since it is larger than the sum of its proper divisors (1).

208688009 is an equidigital number, since it uses as much as digits as its factorization.

208688009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 55296, while the sum is 41.

The square root of 208688009 is about 14446.0378304918. The cubic root of 208688009 is about 593.1517716226.

The spelling of 208688009 in words is "two hundred eight million, six hundred eighty-eight thousand, nine".