243504661 has 4 divisors (see below), whose sum is σ = 243564300. Its totient is φ = 243445024.

The previous prime is 243504649. The next prime is 243504671. The reversal of 243504661 is 166405342.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166405342 = 2 ⋅83202671.

It can be written as a sum of positive squares in 2 ways, for example, as 153140625 + 90364036 = 12375^2 + 9506^2 .

It is a cyclic number.

It is not a de Polignac number, because 243504661 - 2¹⁷ = 243373589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (243504601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23206 + ... + 32023.

It is an arithmetic number, because the mean of its divisors is an integer number (60891075).

Almost surely, 2^243504661 is an apocalyptic number.

It is an amenable number.

243504661 is a deficient number, since it is larger than the sum of its proper divisors (59639).

243504661 is an equidigital number, since it uses as much as digits as its factorization.

243504661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59638.

The product of its (nonzero) digits is 17280, while the sum is 31.

The square root of 243504661 is about 15604.6358816859. The cubic root of 243504661 is about 624.4568388182.

The spelling of 243504661 in words is "two hundred forty-three million, five hundred four thousand, six hundred sixty-one".