643835906 has 16 divisors (see below), whose sum is σ = 1114036416. Its totient is φ = 273350256.

The previous prime is 643835893. The next prime is 643835923. The reversal of 643835906 is 609538346.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 213401 + ... + 216396.

It is an arithmetic number, because the mean of its divisors is an integer number (69627276).

Almost surely, 2^643835906 is an apocalyptic number.

643835906 is a deficient number, since it is larger than the sum of its proper divisors (470200510).

643835906 is a wasteful number, since it uses less digits than its factorization.

643835906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 429913.

The product of its (nonzero) digits is 466560, while the sum is 44.

The square root of 643835906 is about 25373.9217701955. The cubic root of 643835906 is about 863.4921578704.

The spelling of 643835906 in words is "six hundred forty-three million, eight hundred thirty-five thousand, nine hundred six".