243009721 has 2 divisors, whose sum is σ = 243009722. Its totient is φ = 243009720.

The previous prime is 243009719. The next prime is 243009749. The reversal of 243009721 is 127900342.

243009721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (243009749) can be obtained adding 243009721 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 130416400 + 112593321 = 11420^2 + 10611^2 .

It is a cyclic number.

It is not a de Polignac number, because 243009721 - 2¹ = 243009719 is a prime.

Together with 243009719, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 243009721.

It is not a weakly prime, because it can be changed into another prime (243009761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121504860 + 121504861.

It is an arithmetic number, because the mean of its divisors is an integer number (121504861).

Almost surely, 2^243009721 is an apocalyptic number.

It is an amenable number.

243009721 is a deficient number, since it is larger than the sum of its proper divisors (1).

243009721 is an equidigital number, since it uses as much as digits as its factorization.

243009721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 243009721 is about 15588.7690662220. The cubic root of 243009721 is about 624.0334679959.

The spelling of 243009721 in words is "two hundred forty-three million, nine thousand, seven hundred twenty-one".