8686721 has 2 divisors, whose sum is σ = 8686722. Its totient is φ = 8686720.

The previous prime is 8686703. The next prime is 8686729. The reversal of 8686721 is 1276868.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6250000 + 2436721 = 2500^2 + 1561^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8686721 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (8686729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4343360 + 4343361.

It is an arithmetic number, because the mean of its divisors is an integer number (4343361).

Almost surely, 2^8686721 is an apocalyptic number.

It is an amenable number.

8686721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8686721 is an equidigital number, since it uses as much as digits as its factorization.

8686721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32256, while the sum is 38.

The square root of 8686721 is about 2947.3243798401. The cubic root of 8686721 is about 205.5663182850.

The spelling of 8686721 in words is "eight million, six hundred eighty-six thousand, seven hundred twenty-one".