243665 has 4 divisors (see below), whose sum is σ = 292404. Its totient is φ = 194928.

The previous prime is 243647. The next prime is 243671. The reversal of 243665 is 566342.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 135424 + 108241 = 368^2 + 329^2 .

It is a cyclic number.

It is not a de Polignac number, because 243665 - 2¹⁴ = 227281 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24362 + ... + 24371.

It is an arithmetic number, because the mean of its divisors is an integer number (73101).

2²⁴³⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

243665 is a deficient number, since it is larger than the sum of its proper divisors (48739).

243665 is an equidigital number, since it uses as much as digits as its factorization.

243665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48738.

The product of its digits is 4320, while the sum is 26.

The square root of 243665 is about 493.6243511011. The cubic root of 243665 is about 62.4593869483.

The spelling of 243665 in words is "two hundred forty-three thousand, six hundred sixty-five".