208961309 has 2 divisors, whose sum is σ = 208961310. Its totient is φ = 208961308.

The previous prime is 208961287. The next prime is 208961339. The reversal of 208961309 is 903169802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 201725209 + 7236100 = 14203^2 + 2690^2 .

It is a cyclic number.

It is not a de Polignac number, because 208961309 - 2¹² = 208957213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (208961339) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104480654 + 104480655.

It is an arithmetic number, because the mean of its divisors is an integer number (104480655).

Almost surely, 2^208961309 is an apocalyptic number.

It is an amenable number.

208961309 is a deficient number, since it is larger than the sum of its proper divisors (1).

208961309 is an equidigital number, since it uses as much as digits as its factorization.

208961309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 208961309 is about 14455.4940766478. The cubic root of 208961309 is about 593.4105912598.

The spelling of 208961309 in words is "two hundred eight million, nine hundred sixty-one thousand, three hundred nine".