643217906 has 8 divisors (see below), whose sum is σ = 1015607280. Its totient is φ = 304682148.

The previous prime is 643217873. The next prime is 643217909. The reversal of 643217906 is 609712346.

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

It is a Harshad number since it is a multiple of its sum of digits (38), and also a Moran number because the ratio is a prime number: 16926787 = 643217906 / (6 + 4 + 3 + 2 + 1 + 7 + 9 + 0 + 6).

It is a self number, because there is not a number n which added to its sum of digits gives 643217906.

It is not an unprimeable number, because it can be changed into a prime (643217909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8463356 + ... + 8463431.

It is an arithmetic number, because the mean of its divisors is an integer number (126950910).

Almost surely, 2^643217906 is an apocalyptic number.

643217906 is a deficient number, since it is larger than the sum of its proper divisors (372389374).

643217906 is a wasteful number, since it uses less digits than its factorization.

643217906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16926808.

The product of its (nonzero) digits is 54432, while the sum is 38.

The square root of 643217906 is about 25361.7409891356. The cubic root of 643217906 is about 863.2157888033.

It can be divided in two parts, 64321 and 7906, that added together give a palindrome (72227).

The spelling of 643217906 in words is "six hundred forty-three million, two hundred seventeen thousand, nine hundred six".