643312209 has 4 divisors (see below), whose sum is σ = 857749616. Its totient is φ = 428874804.

The previous prime is 643312193. The next prime is 643312211. The reversal of 643312209 is 902213346.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 643312209 - 2⁴ = 643312193 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (643312009) 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, 107218699 + ... + 107218704.

It is an arithmetic number, because the mean of its divisors is an integer number (214437404).

Almost surely, 2^643312209 is an apocalyptic number.

It is an amenable number.

643312209 is a deficient number, since it is larger than the sum of its proper divisors (214437407).

643312209 is a wasteful number, since it uses less digits than its factorization.

643312209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214437406.

The product of its (nonzero) digits is 7776, while the sum is 30.

The square root of 643312209 is about 25363.6000796417. The cubic root of 643312209 is about 863.2579724655.

The spelling of 643312209 in words is "six hundred forty-three million, three hundred twelve thousand, two hundred nine".