647442809 has 4 divisors (see below), whose sum is σ = 697246116. Its totient is φ = 597639504.

The previous prime is 647442797. The next prime is 647442833. The reversal of 647442809 is 908244746.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 38093584 + 609349225 = 6172^2 + 24685^2 .

It is a cyclic number.

It is not a de Polignac number, because 647442809 - 2⁴ = 647442793 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 647442809.

It is not an unprimeable number, because it can be changed into a prime (647442889) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24901634 + ... + 24901659.

It is an arithmetic number, because the mean of its divisors is an integer number (174311529).

Almost surely, 2^647442809 is an apocalyptic number.

It is an amenable number.

647442809 is a deficient number, since it is larger than the sum of its proper divisors (49803307).

647442809 is a wasteful number, since it uses less digits than its factorization.

647442809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49803306.

The product of its (nonzero) digits is 387072, while the sum is 44.

The square root of 647442809 is about 25444.8975042149. The cubic root of 647442809 is about 865.1016437519.

The spelling of 647442809 in words is "six hundred forty-seven million, four hundred forty-two thousand, eight hundred nine".