21043543 has 2 divisors, whose sum is σ = 21043544. Its totient is φ = 21043542.

The previous prime is 21043523. The next prime is 21043549. The reversal of 21043543 is 34534012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21043543 - 2¹⁷ = 20912471 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21043549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521771 + 10521772.

It is an arithmetic number, because the mean of its divisors is an integer number (10521772).

Almost surely, 2^21043543 is an apocalyptic number.

21043543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21043543 is an equidigital number, since it uses as much as digits as its factorization.

21043543 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 22.

The square root of 21043543 is about 4587.3241655675. The cubic root of 21043543 is about 276.0829714488.

Adding to 21043543 its reverse (34534012), we get a palindrome (55577555).

The spelling of 21043543 in words is "twenty-one million, forty-three thousand, five hundred forty-three".