643408165 has 4 divisors (see below), whose sum is σ = 772089804. Its totient is φ = 514726528.

The previous prime is 643408159. The next prime is 643408189. The reversal of 643408165 is 561804346.

It is a happy number.

643408165 is digitally balanced in base 6, 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.

It can be written as a sum of positive squares in 2 ways, for example, as 177582276 + 465825889 = 13326^2 + 21583^2 .

It is a cyclic number.

It is not a de Polignac number, because 643408165 - 2⁷ = 643408037 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64340812 + ... + 64340821.

It is an arithmetic number, because the mean of its divisors is an integer number (193022451).

Almost surely, 2^643408165 is an apocalyptic number.

It is an amenable number.

643408165 is a deficient number, since it is larger than the sum of its proper divisors (128681639).

643408165 is a wasteful number, since it uses less digits than its factorization.

643408165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128681638.

The product of its (nonzero) digits is 69120, while the sum is 37.

The square root of 643408165 is about 25365.4916175500. The cubic root of 643408165 is about 863.3008913171.

The spelling of 643408165 in words is "six hundred forty-three million, four hundred eight thousand, one hundred sixty-five".