681856391 has 8 divisors (see below), whose sum is σ = 684275904. Its totient is φ = 679442400.

The previous prime is 681856379. The next prime is 681856397. The reversal of 681856391 is 193658186.

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 681856391 - 2⁶ = 681856327 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681856397) 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 in 7 ways as a sum of consecutive naturals, for example, 513170 + ... + 514496.

It is an arithmetic number, because the mean of its divisors is an integer number (85534488).

Almost surely, 2^681856391 is an apocalyptic number.

681856391 is a deficient number, since it is larger than the sum of its proper divisors (2419513).

681856391 is a wasteful number, since it uses less digits than its factorization.

681856391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2761.

The product of its digits is 311040, while the sum is 47.

The square root of 681856391 is about 26112.3800332333. The cubic root of 681856391 is about 880.1654264590.

The spelling of 681856391 in words is "six hundred eighty-one million, eight hundred fifty-six thousand, three hundred ninety-one".