21243043 has 4 divisors (see below), whose sum is σ = 21761208. Its totient is φ = 20724880.

The previous prime is 21243023. The next prime is 21243049. The reversal of 21243043 is 34034212.

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

It is a cyclic number.

It is not a de Polignac number, because 21243043 - 2⁵ = 21243011 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21243043.

It is not an unprimeable number, because it can be changed into a prime (21243049) 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, 259021 + ... + 259102.

It is an arithmetic number, because the mean of its divisors is an integer number (5440302).

Almost surely, 2^21243043 is an apocalyptic number.

21243043 is a deficient number, since it is larger than the sum of its proper divisors (518165).

21243043 is an equidigital number, since it uses as much as digits as its factorization.

21243043 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 518164.

The product of its (nonzero) digits is 576, while the sum is 19.

The square root of 21243043 is about 4609.0175742776. The cubic root of 21243043 is about 276.9526825561.

Adding to 21243043 its reverse (34034212), we get a palindrome (55277255).

The spelling of 21243043 in words is "twenty-one million, two hundred forty-three thousand, forty-three".