21605543 has 8 divisors (see below), whose sum is σ = 22377600. Its totient is φ = 20838240.

The previous prime is 21605531. The next prime is 21605561. The reversal of 21605543 is 34550612.

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

It is a cyclic number.

It is not a de Polignac number, because 21605543 - 2¹⁴ = 21589159 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605593) 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 in 7 ways as a sum of consecutive naturals, for example, 9821 + ... + 11817.

It is an arithmetic number, because the mean of its divisors is an integer number (2797200).

Almost surely, 2^21605543 is an apocalyptic number.

21605543 is a deficient number, since it is larger than the sum of its proper divisors (772057).

21605543 is a wasteful number, since it uses less digits than its factorization.

21605543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2377.

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 21605543 is about 4648.1763090485. The cubic root of 21605543 is about 278.5191505042.

The spelling of 21605543 in words is "twenty-one million, six hundred five thousand, five hundred forty-three".