243213991 has 2 divisors, whose sum is σ = 243213992. Its totient is φ = 243213990.

The previous prime is 243213947. The next prime is 243214043. The reversal of 243213991 is 199312342.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 243213991 - 2¹⁵ = 243181223 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243210991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121606995 + 121606996.

It is an arithmetic number, because the mean of its divisors is an integer number (121606996).

Almost surely, 2^243213991 is an apocalyptic number.

243213991 is a deficient number, since it is larger than the sum of its proper divisors (1).

243213991 is an equidigital number, since it uses as much as digits as its factorization.

243213991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11664, while the sum is 34.

The square root of 243213991 is about 15595.3195222156. The cubic root of 243213991 is about 624.2082698048.

The spelling of 243213991 in words is "two hundred forty-three million, two hundred thirteen thousand, nine hundred ninety-one".