243840 has 64 divisors (see below), whose sum is σ = 783360. Its totient is φ = 64512.

The previous prime is 243839. The next prime is 243851. The reversal of 243840 is 48342.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (64).

It is an Ulam number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1857 + ... + 1983.

It is an arithmetic number, because the mean of its divisors is an integer number (12240).

2²⁴³⁸⁴⁰ is an apocalyptic number.

243840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 243840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (391680).

243840 is an abundant number, since it is smaller than the sum of its proper divisors (539520).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

243840 is a wasteful number, since it uses less digits than its factorization.

243840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 149 (or 137 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 21.

The square root of 243840 is about 493.8015795844. The cubic root of 243840 is about 62.4743361300.

The spelling of 243840 in words is "two hundred forty-three thousand, eight hundred forty".