681809 has 2 divisors, whose sum is σ = 681810. Its totient is φ = 681808.

The previous prime is 681787. The next prime is 681823. The reversal of 681809 is 908186.

681809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 672400 + 9409 = 820^2 + 97^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681809 is a prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 681809.

It is not a weakly prime, because it can be changed into another prime (681839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340904 + 340905.

It is an arithmetic number, because the mean of its divisors is an integer number (340905).

2⁶⁸¹⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

681809 is a deficient number, since it is larger than the sum of its proper divisors (1).

681809 is an equidigital number, since it uses as much as digits as its factorization.

681809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 681809 is about 825.7172639590. The cubic root of 681809 is about 88.0145034635.

The spelling of 681809 in words is "six hundred eighty-one thousand, eight hundred nine".