21166543 has 4 divisors (see below), whose sum is σ = 21181680. Its totient is φ = 21151408.

The previous prime is 21166529. The next prime is 21166559. The reversal of 21166543 is 34566112.

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 21166543 - 2⁵ = 21166511 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 (21166643) 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, 5230 + ... + 8347.

It is an arithmetic number, because the mean of its divisors is an integer number (5295420).

Almost surely, 2^21166543 is an apocalyptic number.

21166543 is a deficient number, since it is larger than the sum of its proper divisors (15137).

21166543 is a wasteful number, since it uses less digits than its factorization.

21166543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15136.

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

The square root of 21166543 is about 4600.7111406825. The cubic root of 21166543 is about 276.6198306227.

The spelling of 21166543 in words is "twenty-one million, one hundred sixty-six thousand, five hundred forty-three".