21708443 has 4 divisors (see below), whose sum is σ = 22457040. Its totient is φ = 20959848.

The previous prime is 21708437. The next prime is 21708451. The reversal of 21708443 is 34480712.

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 21708443 - 2⁸ = 21708187 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 748567 = 21708443 / (2 + 1 + 7 + 0 + 8 + 4 + 4 + 3).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21708413) 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, 374255 + ... + 374312.

It is an arithmetic number, because the mean of its divisors is an integer number (5614260).

Almost surely, 2^21708443 is an apocalyptic number.

21708443 is a deficient number, since it is larger than the sum of its proper divisors (748597).

21708443 is an equidigital number, since it uses as much as digits as its factorization.

21708443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 748596.

The product of its (nonzero) digits is 5376, while the sum is 29.

The square root of 21708443 is about 4659.2320182622. The cubic root of 21708443 is about 278.9606150218.

The spelling of 21708443 in words is "twenty-one million, seven hundred eight thousand, four hundred forty-three".