643784664 has 32 divisors (see below), whose sum is σ = 1631513520. Its totient is φ = 211654656.

The previous prime is 643784663. The next prime is 643784671. The reversal of 643784664 is 466487346.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643784663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 181977 + ... + 185480.

Almost surely, 2^643784664 is an apocalyptic number.

It is an amenable number.

643784664 is an abundant number, since it is smaller than the sum of its proper divisors (987728856).

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

643784664 is a wasteful number, since it uses less digits than its factorization.

643784664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 367539 (or 367535 counting only the distinct ones).

The product of its digits is 2322432, while the sum is 48.

The square root of 643784664 is about 25372.9120126169. The cubic root of 643784664 is about 863.4692492179.

The spelling of 643784664 in words is "six hundred forty-three million, seven hundred eighty-four thousand, six hundred sixty-four".