681558209 has 2 divisors, whose sum is σ = 681558210. Its totient is φ = 681558208.

The previous prime is 681558197. The next prime is 681558247. The reversal of 681558209 is 902855186.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 679749184 + 1809025 = 26072^2 + 1345^2 .

It is a cyclic number.

It is not a de Polignac number, because 681558209 - 2¹⁶ = 681492673 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 681558209.

It is not a weakly prime, because it can be changed into another prime (681558259) 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, 340779104 + 340779105.

It is an arithmetic number, because the mean of its divisors is an integer number (340779105).

Almost surely, 2^681558209 is an apocalyptic number.

It is an amenable number.

681558209 is a deficient number, since it is larger than the sum of its proper divisors (1).

681558209 is an equidigital number, since it uses as much as digits as its factorization.

681558209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 172800, while the sum is 44.

The square root of 681558209 is about 26106.6698182667. The cubic root of 681558209 is about 880.0371063038.

The spelling of 681558209 in words is "six hundred eighty-one million, five hundred fifty-eight thousand, two hundred nine".