243636561 has 24 divisors (see below), whose sum is σ = 402966720. Its totient is φ = 138953376.

The previous prime is 243636557. The next prime is 243636583. The reversal of 243636561 is 165636342.

It is not a de Polignac number, because 243636561 - 2² = 243636557 is a prime.

It is not an unprimeable number, because it can be changed into a prime (243636541) 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 23 ways as a sum of consecutive naturals, for example, 32035 + ... + 38903.

It is an arithmetic number, because the mean of its divisors is an integer number (16790280).

Almost surely, 2^243636561 is an apocalyptic number.

243636561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

243636561 is a deficient number, since it is larger than the sum of its proper divisors (159330159).

243636561 is a wasteful number, since it uses less digits than its factorization.

243636561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7445 (or 7442 counting only the distinct ones).

The product of its digits is 77760, while the sum is 36.

The square root of 243636561 is about 15608.8616176837. The cubic root of 243636561 is about 624.5695690214.

It can be divided in two parts, 243 and 636561, that added together give a square (636804 = 798²).

The spelling of 243636561 in words is "two hundred forty-three million, six hundred thirty-six thousand, five hundred sixty-one".