681897809 has 2 divisors, whose sum is σ = 681897810. Its totient is φ = 681897808.

The previous prime is 681897739. The next prime is 681897817. The reversal of 681897809 is 908798186.

It is a happy number.

681897809 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., 613057600 + 68840209 = 24760^2 + 8297^2 .

It is a cyclic number.

It is not a de Polignac number, because 681897809 - 2¹² = 681893713 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (681897899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340948904 + 340948905.

It is an arithmetic number, because the mean of its divisors is an integer number (340948905).

Almost surely, 2^681897809 is an apocalyptic number.

It is an amenable number.

681897809 is a deficient number, since it is larger than the sum of its proper divisors (1).

681897809 is an equidigital number, since it uses as much as digits as its factorization.

681897809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1741824, while the sum is 56.

The square root of 681897809 is about 26113.1730932876. The cubic root of 681897809 is about 880.1832473931.

The spelling of 681897809 in words is "six hundred eighty-one million, eight hundred ninety-seven thousand, eight hundred nine".