21706543 has 4 divisors (see below), whose sum is σ = 21747208. Its totient is φ = 21665880.

The previous prime is 21706537. The next prime is 21706561. The reversal of 21706543 is 34560712.

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 21706543 - 2⁹ = 21706031 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 (21706523) 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, 19521 + ... + 20602.

It is an arithmetic number, because the mean of its divisors is an integer number (5436802).

Almost surely, 2^21706543 is an apocalyptic number.

21706543 is a deficient number, since it is larger than the sum of its proper divisors (40665).

21706543 is an equidigital number, since it uses as much as digits as its factorization.

21706543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40664.

The product of its (nonzero) digits is 5040, while the sum is 28.

The square root of 21706543 is about 4659.0281175370. The cubic root of 21706543 is about 278.9524762432.

The spelling of 21706543 in words is "twenty-one million, seven hundred six thousand, five hundred forty-three".