243909561 has 16 divisors (see below), whose sum is σ = 372031488. Its totient is φ = 139242000.

The previous prime is 243909559. The next prime is 243909607. The reversal of 243909561 is 165909342.

It is not a de Polignac number, because 243909561 - 2¹ = 243909559 is a prime.

It is not an unprimeable number, because it can be changed into a prime (243909161) 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, 19126 + ... + 29216.

It is an arithmetic number, because the mean of its divisors is an integer number (23251968).

Almost surely, 2^243909561 is an apocalyptic number.

243909561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

243909561 is a deficient number, since it is larger than the sum of its proper divisors (128121927).

243909561 is a wasteful number, since it uses less digits than its factorization.

243909561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11252.

The product of its (nonzero) digits is 58320, while the sum is 39.

The square root of 243909561 is about 15617.6042016693. The cubic root of 243909561 is about 624.8027631494.

The spelling of 243909561 in words is "two hundred forty-three million, nine hundred nine thousand, five hundred sixty-one".