243243821 has 2 divisors, whose sum is σ = 243243822. Its totient is φ = 243243820.

The previous prime is 243243779. The next prime is 243243823. The reversal of 243243821 is 128342342.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 183738025 + 59505796 = 13555^2 + 7714^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-243243821 is a prime.

Together with 243243823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243243823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121621910 + 121621911.

It is an arithmetic number, because the mean of its divisors is an integer number (121621911).

Almost surely, 2^243243821 is an apocalyptic number.

It is an amenable number.

243243821 is a deficient number, since it is larger than the sum of its proper divisors (1).

243243821 is an equidigital number, since it uses as much as digits as its factorization.

243243821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9216, while the sum is 29.

The square root of 243243821 is about 15596.2758695786. The cubic root of 243243821 is about 624.2337883086.

The spelling of 243243821 in words is "two hundred forty-three million, two hundred forty-three thousand, eight hundred twenty-one".