243921 has 4 divisors (see below), whose sum is σ = 325232. Its totient is φ = 162612.

The previous prime is 243917. The next prime is 243931. The reversal of 243921 is 129342.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 243921 - 2² = 243917 is a prime.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (243911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40651 + ... + 40656.

It is an arithmetic number, because the mean of its divisors is an integer number (81308).

2²⁴³⁹²¹ is an apocalyptic number.

It is an amenable number.

243921 is a deficient number, since it is larger than the sum of its proper divisors (81311).

243921 is an equidigital number, since it uses as much as digits as its factorization.

243921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81310.

The product of its digits is 432, while the sum is 21.

The square root of 243921 is about 493.8835895229. The cubic root of 243921 is about 62.4812530441.

The spelling of 243921 in words is "two hundred forty-three thousand, nine hundred twenty-one".