643651938 has 12 divisors (see below), whose sum is σ = 1394579238. Its totient is φ = 214550640.

The previous prime is 643651919. The next prime is 643651949. The reversal of 643651938 is 839156346.

643651938 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 332588169 + 311063769 = 18237^2 + 17637^2 .

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 a junction number, because it is equal to n+sod(n) for n = 643651893 and 643651902.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 17879203 + ... + 17879238.

Almost surely, 2^643651938 is an apocalyptic number.

643651938 is an abundant number, since it is smaller than the sum of its proper divisors (750927300).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

643651938 is a wasteful number, since it uses less digits than its factorization.

643651938 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35758449 (or 35758446 counting only the distinct ones).

The product of its digits is 466560, while the sum is 45.

The square root of 643651938 is about 25370.2963719386. The cubic root of 643651938 is about 863.4099060334.

The spelling of 643651938 in words is "six hundred forty-three million, six hundred fifty-one thousand, nine hundred thirty-eight".