8720209 has 3 divisors (see below), whose sum is σ = 8723163. Its totient is φ = 8717256.

The previous prime is 8720191. The next prime is 8720227. The reversal of 8720209 is 9020278.

The square root of 8720209 is 2953.

It is a perfect power (a square), and thus also a powerful number.

8720209 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (8720191) and next prime (8720227).

It can be written as a sum of positive squares in only one way, i.e., 7102225 + 1617984 = 2665^2 + 1272^2 .

It is not a de Polignac number, because 8720209 - 2⁵ = 8720177 is a prime.

It is a Duffinian number.

8720209 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (8720809) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 1477 + ... + 4429.

It is an arithmetic number, because the mean of its divisors is an integer number (2907721).

Almost surely, 2^8720209 is an apocalyptic number.

8720209 is the 2953-rd square number.

8720209 is the 1477-th centered octagonal number.

It is an amenable number.

8720209 is a deficient number, since it is larger than the sum of its proper divisors (2954).

8720209 is an frugal number, since it uses more digits than its factorization.

8720209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5906 (or 2953 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 28.

The cubic root of 8720209 is about 205.8301377261.

The spelling of 8720209 in words is "eight million, seven hundred twenty thousand, two hundred nine".