1686840209 has 2 divisors, whose sum is σ = 1686840210. Its totient is φ = 1686840208.

The previous prime is 1686840161. The next prime is 1686840247. The reversal of 1686840209 is 9020486861.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1052807809 + 634032400 = 32447^2 + 25180^2 .

It is an emirp because it is prime and its reverse (9020486861) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1686840209 - 2²⁴ = 1670062993 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1686840209.

It is not a weakly prime, because it can be changed into another prime (1686840269) 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, 843420104 + 843420105.

It is an arithmetic number, because the mean of its divisors is an integer number (843420105).

Almost surely, 2^1686840209 is an apocalyptic number.

It is an amenable number.

1686840209 is a deficient number, since it is larger than the sum of its proper divisors (1).

1686840209 is an equidigital number, since it uses as much as digits as its factorization.

1686840209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 165888, while the sum is 44.

The square root of 1686840209 is about 41071.1603074469. The cubic root of 1686840209 is about 1190.3956053528.

The spelling of 1686840209 in words is "one billion, six hundred eighty-six million, eight hundred forty thousand, two hundred nine".