647855209 has 3 divisors (see below), whose sum is σ = 647880663. Its totient is φ = 647829756.

The previous prime is 647855207. The next prime is 647855233. The reversal of 647855209 is 902558746.

The square root of 647855209 is 25453.

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

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, and also an emirpimes, since its reverse is a distinct semiprime: 902558746 = 2 ⋅451279373.

It can be written as a sum of positive squares in only one way, i.e., 315595225 + 332259984 = 17765^2 + 18228^2 .

It is not a de Polignac number, because 647855209 - 2¹ = 647855207 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (647855207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 12727 + ... + 38179.

It is an arithmetic number, because the mean of its divisors is an integer number (215960221).

Almost surely, 2^647855209 is an apocalyptic number.

647855209 is the 25453-rd square number.

647855209 is the 12727-th centered octagonal number.

It is an amenable number.

647855209 is a deficient number, since it is larger than the sum of its proper divisors (25454).

647855209 is an frugal number, since it uses more digits than its factorization.

647855209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50906 (or 25453 counting only the distinct ones).

The product of its (nonzero) digits is 604800, while the sum is 46.

The cubic root of 647855209 is about 865.2852852977.

The spelling of 647855209 in words is "six hundred forty-seven million, eight hundred fifty-five thousand, two hundred nine".