643687643 has 8 divisors (see below), whose sum is σ = 717423120. Its totient is φ = 573937920.

The previous prime is 643687613. The next prime is 643687651. The reversal of 643687643 is 346786346.

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

It is a cyclic number.

It is not a de Polignac number, because 643687643 - 2⁶ = 643687579 is a prime.

It is not an unprimeable number, because it can be changed into a prime (643687613) 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, 996098 + ... + 996743.

It is an arithmetic number, because the mean of its divisors is an integer number (89677890).

Almost surely, 2^643687643 is an apocalyptic number.

643687643 is a deficient number, since it is larger than the sum of its proper divisors (73735477).

643687643 is a wasteful number, since it uses less digits than its factorization.

643687643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1992877.

The product of its digits is 1741824, while the sum is 47.

The square root of 643687643 is about 25371.0000394151. Note that the first 4 decimals coincide. The cubic root of 643687643 is about 863.4258709148.

The spelling of 643687643 in words is "six hundred forty-three million, six hundred eighty-seven thousand, six hundred forty-three".