647549809 has 3 divisors (see below), whose sum is σ = 647575257. Its totient is φ = 647524362.

The previous prime is 647549803. The next prime is 647549821. The reversal of 647549809 is 908945746.

It is a happy number.

The square root of 647549809 is 25447.

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

647549809 is digitally balanced in base 2, 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, and also an emirpimes, since its reverse is a distinct semiprime: 908945746 = 2 ⋅454472873.

It is not a de Polignac number, because 647549809 - 2³ = 647549801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (647549801) 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, 12724 + ... + 38170.

It is an arithmetic number, because the mean of its divisors is an integer number (215858419).

Almost surely, 2^647549809 is an apocalyptic number.

647549809 is the 25447-th square number.

647549809 is the 12724-th centered octagonal number.

It is an amenable number.

647549809 is a deficient number, since it is larger than the sum of its proper divisors (25448).

647549809 is an frugal number, since it uses more digits than its factorization.

647549809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50894 (or 25447 counting only the distinct ones).

The product of its (nonzero) digits is 2177280, while the sum is 52.

The cubic root of 647549809 is about 865.1492982967.

The spelling of 647549809 in words is "six hundred forty-seven million, five hundred forty-nine thousand, eight hundred nine".