243616721 has 2 divisors, whose sum is σ = 243616722. Its totient is φ = 243616720.

The previous prime is 243616717. The next prime is 243616739. The reversal of 243616721 is 127616342.

243616721 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., 147282496 + 96334225 = 12136^2 + 9815^2 .

It is a cyclic number.

It is not a de Polignac number, because 243616721 - 2² = 243616717 is a prime.

It is not a weakly prime, because it can be changed into another prime (243616741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121808360 + 121808361.

It is an arithmetic number, because the mean of its divisors is an integer number (121808361).

Almost surely, 2^243616721 is an apocalyptic number.

It is an amenable number.

243616721 is a deficient number, since it is larger than the sum of its proper divisors (1).

243616721 is an equidigital number, since it uses as much as digits as its factorization.

243616721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 32.

The square root of 243616721 is about 15608.2260683269. The cubic root of 243616721 is about 624.5526150845.

The spelling of 243616721 in words is "two hundred forty-three million, six hundred sixteen thousand, seven hundred twenty-one".