21043205 has 4 divisors (see below), whose sum is σ = 25251852. Its totient is φ = 16834560.

The previous prime is 21043177. The next prime is 21043207. The reversal of 21043205 is 50234012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9746884 + 11296321 = 3122^2 + 3361^2 .

It is not a de Polignac number, because 21043205 - 2¹⁴ = 21026821 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 (21043207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2104316 + ... + 2104325.

It is an arithmetic number, because the mean of its divisors is an integer number (6312963).

Almost surely, 2^21043205 is an apocalyptic number.

It is an amenable number.

21043205 is a deficient number, since it is larger than the sum of its proper divisors (4208647).

21043205 is an equidigital number, since it uses as much as digits as its factorization.

21043205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4208646.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21043205 is about 4587.2873247705. The cubic root of 21043205 is about 276.0814932988.

Adding to 21043205 its reverse (50234012), we get a palindrome (71277217).

The spelling of 21043205 in words is "twenty-one million, forty-three thousand, two hundred five".