681813991 has 4 divisors (see below), whose sum is σ = 683874184. Its totient is φ = 679753800.

The previous prime is 681813967. The next prime is 681814033. The reversal of 681813991 is 199318186.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 681813991 - 2⁹ = 681813479 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 (681813901) 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, 1029600 + ... + 1030261.

It is an arithmetic number, because the mean of its divisors is an integer number (170968546).

Almost surely, 2^681813991 is an apocalyptic number.

681813991 is a deficient number, since it is larger than the sum of its proper divisors (2060193).

681813991 is a wasteful number, since it uses less digits than its factorization.

681813991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2060192.

The product of its digits is 93312, while the sum is 46.

The square root of 681813991 is about 26111.5681451727. The cubic root of 681813991 is about 880.1471822519.

The spelling of 681813991 in words is "six hundred eighty-one million, eight hundred thirteen thousand, nine hundred ninety-one".