21409543 has 2 divisors, whose sum is σ = 21409544. Its totient is φ = 21409542.

The previous prime is 21409541. The next prime is 21409559. The reversal of 21409543 is 34590412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21409543 - 2¹ = 21409541 is a prime.

Together with 21409541, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21409541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10704771 + 10704772.

It is an arithmetic number, because the mean of its divisors is an integer number (10704772).

Almost surely, 2^21409543 is an apocalyptic number.

21409543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21409543 is an equidigital number, since it uses as much as digits as its factorization.

21409543 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21409543 is about 4627.0447371946. The cubic root of 21409543 is about 277.6743724564.

Adding to 21409543 its reverse (34590412), we get a palindrome (55999955).

It can be divided in two parts, 21409 and 543, that added together give a cube (21952 = 28³).

The spelling of 21409543 in words is "twenty-one million, four hundred nine thousand, five hundred forty-three".