686176721 has 2 divisors, whose sum is σ = 686176722. Its totient is φ = 686176720.

The previous prime is 686176717. The next prime is 686176741. The reversal of 686176721 is 127671686.

686176721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 468289600 + 217887121 = 21640^2 + 14761^2 .

It is a cyclic number.

It is not a de Polignac number, because 686176721 - 2² = 686176717 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (686176741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343088360 + 343088361.

It is an arithmetic number, because the mean of its divisors is an integer number (343088361).

Almost surely, 2^686176721 is an apocalyptic number.

It is an amenable number.

686176721 is a deficient number, since it is larger than the sum of its proper divisors (1).

686176721 is an equidigital number, since it uses as much as digits as its factorization.

686176721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 169344, while the sum is 44.

The square root of 686176721 is about 26194.9751097419. The cubic root of 686176721 is about 882.0204612499.

The spelling of 686176721 in words is "six hundred eighty-six million, one hundred seventy-six thousand, seven hundred twenty-one".