681668391 has 8 divisors (see below), whose sum is σ = 912695040. Its totient is φ = 452543672.

The previous prime is 681668389. The next prime is 681668399. The reversal of 681668391 is 193866186.

681668391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 681668391 - 2¹ = 681668389 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 681668391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681668399) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 474645 + ... + 476078.

It is an arithmetic number, because the mean of its divisors is an integer number (114086880).

Almost surely, 2^681668391 is an apocalyptic number.

681668391 is a deficient number, since it is larger than the sum of its proper divisors (231026649).

681668391 is a wasteful number, since it uses less digits than its factorization.

681668391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 950965.

The product of its digits is 373248, while the sum is 48.

The square root of 681668391 is about 26108.7799600058. The cubic root of 681668391 is about 880.0845265742.

The spelling of 681668391 in words is "six hundred eighty-one million, six hundred sixty-eight thousand, three hundred ninety-one".