664840809 has 12 divisors (see below), whose sum is σ = 967888896. Its totient is φ = 439736472.

The previous prime is 664840807. The next prime is 664840817. The reversal of 664840809 is 908048466.

It is a happy number.

It is not a de Polignac number, because 664840809 - 2¹ = 664840807 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (664840807) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 289689 + ... + 291974.

It is an arithmetic number, because the mean of its divisors is an integer number (80657408).

Almost surely, 2^664840809 is an apocalyptic number.

It is an amenable number.

664840809 is a deficient number, since it is larger than the sum of its proper divisors (303048087).

664840809 is a wasteful number, since it uses less digits than its factorization.

664840809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 581796 (or 581793 counting only the distinct ones).

The product of its (nonzero) digits is 331776, while the sum is 45.

The square root of 664840809 is about 25784.5071506127. The cubic root of 664840809 is about 872.7822187559.

The spelling of 664840809 in words is "six hundred sixty-four million, eight hundred forty thousand, eight hundred nine".