643533643 has 4 divisors (see below), whose sum is σ = 643585288. Its totient is φ = 643482000.

The previous prime is 643533641. The next prime is 643533647. The reversal of 643533643 is 346335346.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 643533643 - 2¹ = 643533641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643533641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5680 + ... + 36322.

It is an arithmetic number, because the mean of its divisors is an integer number (160896322).

Almost surely, 2^643533643 is an apocalyptic number.

643533643 is a deficient number, since it is larger than the sum of its proper divisors (51645).

643533643 is a wasteful number, since it uses less digits than its factorization.

643533643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51644.

The product of its digits is 233280, while the sum is 37.

The square root of 643533643 is about 25367.9648966960. The cubic root of 643533643 is about 863.3570082240.

Adding to 643533643 its reverse (346335346), we get a palindrome (989868989).

The spelling of 643533643 in words is "six hundred forty-three million, five hundred thirty-three thousand, six hundred forty-three".