8720809 has 2 divisors, whose sum is σ = 8720810. Its totient is φ = 8720808.

The previous prime is 8720807. The next prime is 8720819. The reversal of 8720809 is 9080278.

It is a happy number.

8720809 is digitally balanced in base 3, 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., 8294400 + 426409 = 2880^2 + 653^2 .

It is a cyclic number.

It is not a de Polignac number, because 8720809 - 2¹ = 8720807 is a prime.

It is a super-2 number, since 2×8720809² = 152105019228962, which contains 22 as substring.

Together with 8720807, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (8720807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4360404 + 4360405.

It is an arithmetic number, because the mean of its divisors is an integer number (4360405).

Almost surely, 2^8720809 is an apocalyptic number.

It is an amenable number.

8720809 is a deficient number, since it is larger than the sum of its proper divisors (1).

8720809 is an equidigital number, since it uses as much as digits as its factorization.

8720809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 34.

The square root of 8720809 is about 2953.1015898543. The cubic root of 8720809 is about 205.8348583794.

The spelling of 8720809 in words is "eight million, seven hundred twenty thousand, eight hundred nine".