21043305 has 12 divisors (see below), whose sum is σ = 36475140. Its totient is φ = 11223072.

The previous prime is 21043301. The next prime is 21043313. The reversal of 21043305 is 50334012.

It can be written as a sum of positive squares in 2 ways, for example, as 2277081 + 18766224 = 1509^2 + 4332^2 .

It is not a de Polignac number, because 21043305 - 2² = 21043301 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21043301) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 233770 + ... + 233859.

It is an arithmetic number, because the mean of its divisors is an integer number (3039595).

Almost surely, 2^21043305 is an apocalyptic number.

It is an amenable number.

21043305 is a deficient number, since it is larger than the sum of its proper divisors (15431835).

21043305 is a wasteful number, since it uses less digits than its factorization.

21043305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 467640 (or 467637 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 18.

The square root of 21043305 is about 4587.2982244454. The cubic root of 21043305 is about 276.0819306229.

Adding to 21043305 its reverse (50334012), we get a palindrome (71377317).

The spelling of 21043305 in words is "twenty-one million, forty-three thousand, three hundred five".