643542209 has 2 divisors, whose sum is σ = 643542210. Its totient is φ = 643542208.

The previous prime is 643542199. The next prime is 643542233. The reversal of 643542209 is 902245346.

643542209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 621405184 + 22137025 = 24928^2 + 4705^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643542209 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (643542269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321771104 + 321771105.

It is an arithmetic number, because the mean of its divisors is an integer number (321771105).

Almost surely, 2^643542209 is an apocalyptic number.

It is an amenable number.

643542209 is a deficient number, since it is larger than the sum of its proper divisors (1).

643542209 is an equidigital number, since it uses as much as digits as its factorization.

643542209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 51840, while the sum is 35.

The square root of 643542209 is about 25368.1337311202. The cubic root of 643542209 is about 863.3608388879.

The spelling of 643542209 in words is "six hundred forty-three million, five hundred forty-two thousand, two hundred nine".