243213409 has 2 divisors, whose sum is σ = 243213410. Its totient is φ = 243213408.

The previous prime is 243213371. The next prime is 243213457. The reversal of 243213409 is 904312342.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 131446225 + 111767184 = 11465^2 + 10572^2 .

It is a cyclic number.

It is not a de Polignac number, because 243213409 - 2¹⁹ = 242689121 is a prime.

It is not a weakly prime, because it can be changed into another prime (243213499) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121606704 + 121606705.

It is an arithmetic number, because the mean of its divisors is an integer number (121606705).

Almost surely, 2^243213409 is an apocalyptic number.

It is an amenable number.

243213409 is a deficient number, since it is larger than the sum of its proper divisors (1).

243213409 is an equidigital number, since it uses as much as digits as its factorization.

243213409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 28.

The square root of 243213409 is about 15595.3008627599. The cubic root of 243213409 is about 624.2077719037.

It can be divided in two parts, 24321 and 3409, that added together give a triangular number (27730 = T₂₃₅).

The spelling of 243213409 in words is "two hundred forty-three million, two hundred thirteen thousand, four hundred nine".