• Sorting the digits of 2²⁴³ and those of F₂₄₃ in ascending order we obtain two prime numbers (of 65 and 50 digits, respectively).

• 243 can be written using four 4's:

See also 113.

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243 has 6 divisors (see below), whose sum is σ = 364. Its totient is φ = 162.

The previous prime is 241. The next prime is 251. The reversal of 243 is 342.

It is a perfect power (a 5-th power), and thus also a powerful number.

243 is nontrivially palindromic in base 8.

It is not a de Polignac number, because 243 - 2¹ = 241 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is an Ulam number.

It is a Duffinian number.

243 is an undulating number in base 8.

Its product of digits (24) is a multiple of the sum of its prime divisors (3).

It is a plaindrome in base 13, base 14 and base 15.

It is a nialpdrome in base 3, base 9 and base 16.

It is a zygodrome in base 2.

It is not an unprimeable number, because it can be changed into a prime (241) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 80 + 81 + 82.

2²⁴³ is an apocalyptic number.

243 is a deficient number, since it is larger than the sum of its proper divisors (121).

243 is an frugal number, since it uses more digits than its factorization.

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

The sum of its prime factors is 15 (or 3 counting only the distinct ones).

The product of its digits is 24, while the sum is 9.

The square root of 243 is about 15.5884572681. The cubic root of 243 is about 6.2402514692.

Multiplying 243 by its product of digits (24), we get a cube (5832 = 18³).

Adding to 243 its reverse (342), we get a palindrome (585).

Subtracting 243 from its reverse (342), we obtain a palindrome (99).

It can be divided in two parts, 24 and 3, that added together give a cube (27 = 3³).

The spelling of 243 in words is "two hundred forty-three", and thus it is an aban number and an iban number.