681306809 has 4 divisors (see below), whose sum is σ = 703284480. Its totient is φ = 659329140.

The previous prime is 681306803. The next prime is 681306811. The reversal of 681306809 is 908603186.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681306809 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (681306803) 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 in 3 ways as a sum of consecutive naturals, for example, 10988789 + ... + 10988850.

It is an arithmetic number, because the mean of its divisors is an integer number (175821120).

Almost surely, 2^681306809 is an apocalyptic number.

It is an amenable number.

681306809 is a deficient number, since it is larger than the sum of its proper divisors (21977671).

681306809 is a wasteful number, since it uses less digits than its factorization.

681306809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21977670.

The product of its (nonzero) digits is 62208, while the sum is 41.

The square root of 681306809 is about 26101.8545126587. The cubic root of 681306809 is about 879.9288893124.

The spelling of 681306809 in words is "six hundred eighty-one million, three hundred six thousand, eight hundred nine".