643930555 has 4 divisors (see below), whose sum is σ = 772716672. Its totient is φ = 515144440.

The previous prime is 643930531. The next prime is 643930561. The reversal of 643930555 is 555039346.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 643930555 - 2²⁹ = 107059643 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64393051 + ... + 64393060.

It is an arithmetic number, because the mean of its divisors is an integer number (193179168).

Almost surely, 2^643930555 is an apocalyptic number.

643930555 is a deficient number, since it is larger than the sum of its proper divisors (128786117).

643930555 is a wasteful number, since it uses less digits than its factorization.

643930555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128786116.

The product of its (nonzero) digits is 243000, while the sum is 40.

The square root of 643930555 is about 25375.7867858319. The cubic root of 643930555 is about 863.5344692025.

The spelling of 643930555 in words is "six hundred forty-three million, nine hundred thirty thousand, five hundred fifty-five".