681816961 has 4 divisors (see below), whose sum is σ = 779219392. Its totient is φ = 584414532.

The previous prime is 681816959. The next prime is 681816979. The reversal of 681816961 is 169618186.

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 not a de Polignac number, because 681816961 - 2¹ = 681816959 is a prime.

It is not an unprimeable number, because it can be changed into a prime (681816061) 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 3 ways as a sum of consecutive naturals, for example, 48701205 + ... + 48701218.

It is an arithmetic number, because the mean of its divisors is an integer number (194804848).

Almost surely, 2^681816961 is an apocalyptic number.

It is an amenable number.

681816961 is a deficient number, since it is larger than the sum of its proper divisors (97402431).

681816961 is an equidigital number, since it uses as much as digits as its factorization.

681816961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97402430.

The product of its digits is 124416, while the sum is 46.

The square root of 681816961 is about 26111.6250164558. The cubic root of 681816961 is about 880.1484602316.

The spelling of 681816961 in words is "six hundred eighty-one million, eight hundred sixteen thousand, nine hundred sixty-one".