243128561 has 16 divisors (see below), whose sum is σ = 273974400. Its totient is φ = 214072320.

The previous prime is 243128551. The next prime is 243128569. The reversal of 243128561 is 165821342.

It is a cyclic number.

It is not a de Polignac number, because 243128561 - 2¹⁰ = 243127537 is a prime.

It is a super-2 number, since 2×243128561² = 118222994347861442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (243128569) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 133346 + ... + 135156.

It is an arithmetic number, because the mean of its divisors is an integer number (17123400).

Almost surely, 2^243128561 is an apocalyptic number.

It is an amenable number.

243128561 is a deficient number, since it is larger than the sum of its proper divisors (30845839).

243128561 is a wasteful number, since it uses less digits than its factorization.

243128561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2296.

The product of its digits is 11520, while the sum is 32.

The square root of 243128561 is about 15592.5803188568. The cubic root of 243128561 is about 624.1351759322.

The spelling of 243128561 in words is "two hundred forty-three million, one hundred twenty-eight thousand, five hundred sixty-one".