243115661 has 2 divisors, whose sum is σ = 243115662. Its totient is φ = 243115660.

The previous prime is 243115643. The next prime is 243115667. The reversal of 243115661 is 166511342.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 242767561 + 348100 = 15581^2 + 590^2 .

It is a cyclic number.

It is not a de Polignac number, because 243115661 - 2¹⁴ = 243099277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243115667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121557830 + 121557831.

It is an arithmetic number, because the mean of its divisors is an integer number (121557831).

Almost surely, 2^243115661 is an apocalyptic number.

It is an amenable number.

243115661 is a deficient number, since it is larger than the sum of its proper divisors (1).

243115661 is an equidigital number, since it uses as much as digits as its factorization.

243115661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 29.

The square root of 243115661 is about 15592.1666550868. The cubic root of 243115661 is about 624.1241372097.

The spelling of 243115661 in words is "two hundred forty-three million, one hundred fifteen thousand, six hundred sixty-one".