21388443 has 4 divisors (see below), whose sum is σ = 28517928. Its totient is φ = 14258960.

The previous prime is 21388441. The next prime is 21388447. The reversal of 21388443 is 34488312.

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 21388443 - 2¹ = 21388441 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21388441) 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 3 ways as a sum of consecutive naturals, for example, 3564738 + ... + 3564743.

It is an arithmetic number, because the mean of its divisors is an integer number (7129482).

Almost surely, 2^21388443 is an apocalyptic number.

21388443 is a deficient number, since it is larger than the sum of its proper divisors (7129485).

21388443 is an equidigital number, since it uses as much as digits as its factorization.

21388443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7129484.

The product of its digits is 18432, while the sum is 33.

The square root of 21388443 is about 4624.7641020921. The cubic root of 21388443 is about 277.5831225707.

The spelling of 21388443 in words is "twenty-one million, three hundred eighty-eight thousand, four hundred forty-three".