21243 has 8 divisors (see below), whose sum is σ = 29008. Its totient is φ = 13824.

The previous prime is 21227. The next prime is 21247. The reversal of 21243 is 34212.

21243 is nontrivially palindromic in base 9.

21243 is an esthetic number in base 9, because in such base its adjacent digits differ by 1.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21243 - 2⁴ = 21227 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21247) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 171 + ... + 267.

It is an arithmetic number, because the mean of its divisors is an integer number (3626).

2²¹²⁴³ is an apocalyptic number.

21243 is a deficient number, since it is larger than the sum of its proper divisors (7765).

21243 is an equidigital number, since it uses as much as digits as its factorization.

21243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173.

The product of its digits is 48, while the sum is 12.

The square root of 21243 is about 145.7497855916. The cubic root of 21243 is about 27.6952495688.

Adding to 21243 its reverse (34212), we get a palindrome (55455).

The spelling of 21243 in words is "twenty-one thousand, two hundred forty-three", and thus it is an iban number.