643917639 has 8 divisors (see below), whose sum is σ = 864734080. Its totient is φ = 426189816.

The previous prime is 643917613. The next prime is 643917643. The reversal of 643917639 is 936719346.

643917639 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 643917639 - 2¹⁶ = 643852103 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643917649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 771667 + ... + 772500.

It is an arithmetic number, because the mean of its divisors is an integer number (108091760).

Almost surely, 2^643917639 is an apocalyptic number.

643917639 is a deficient number, since it is larger than the sum of its proper divisors (220816441).

643917639 is a wasteful number, since it uses less digits than its factorization.

643917639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1544309.

The product of its digits is 734832, while the sum is 48.

The square root of 643917639 is about 25375.5322899836. The cubic root of 643917639 is about 863.5286955542.

The spelling of 643917639 in words is "six hundred forty-three million, nine hundred seventeen thousand, six hundred thirty-nine".