681722781 has 8 divisors (see below), whose sum is σ = 909147264. Its totient is φ = 454390080.

The previous prime is 681722779. The next prime is 681722791. The reversal of 681722781 is 187227186.

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

It is not a de Polignac number, because 681722781 - 2¹ = 681722779 is a prime.

It is a super-2 number, since 2×681722781² = 929491900268747922, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681722771) 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, 3180 + ... + 37061.

It is an arithmetic number, because the mean of its divisors is an integer number (113643408).

Almost surely, 2^681722781 is an apocalyptic number.

It is an amenable number.

681722781 is a deficient number, since it is larger than the sum of its proper divisors (227424483).

681722781 is a wasteful number, since it uses less digits than its factorization.

681722781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45891.

The product of its digits is 75264, while the sum is 42.

The square root of 681722781 is about 26109.8215428601. The cubic root of 681722781 is about 880.1079331284.

The spelling of 681722781 in words is "six hundred eighty-one million, seven hundred twenty-two thousand, seven hundred eighty-one".