243209 has 2 divisors, whose sum is σ = 243210. Its totient is φ = 243208.

The previous prime is 243203. The next prime is 243227. The reversal of 243209 is 902342.

243209 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., 183184 + 60025 = 428^2 + 245^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-243209 is a prime.

It is a Chen prime.

It is equal to p₂₁₄₈₅ and since 243209 and 21485 have the same sum of digits, it is a Honaker prime.

It is a plaindrome in base 11.

It is not a weakly prime, because it can be changed into another prime (243203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121604 + 121605.

It is an arithmetic number, because the mean of its divisors is an integer number (121605).

2²⁴³²⁰⁹ is an apocalyptic number.

It is an amenable number.

243209 is a deficient number, since it is larger than the sum of its proper divisors (1).

243209 is an equidigital number, since it uses as much as digits as its factorization.

243209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 432, while the sum is 20.

The square root of 243209 is about 493.1622451080. The cubic root of 243209 is about 62.4203999978.

The spelling of 243209 in words is "two hundred forty-three thousand, two hundred nine".