21320305 has 8 divisors (see below), whose sum is σ = 25662312. Its totient is φ = 17004288.

The previous prime is 21320297. The next prime is 21320311. The reversal of 21320305 is 50302312.

It can be written as a sum of positive squares in 4 ways, for example, as 535824 + 20784481 = 732^2 + 4559^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21320305 - 2³ = 21320297 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4642 + ... + 8011.

It is an arithmetic number, because the mean of its divisors is an integer number (3207789).

Almost surely, 2^21320305 is an apocalyptic number.

It is an amenable number.

21320305 is a deficient number, since it is larger than the sum of its proper divisors (4342007).

21320305 is a wasteful number, since it uses less digits than its factorization.

21320305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12995.

The product of its (nonzero) digits is 180, while the sum is 16.

The square root of 21320305 is about 4617.3915796692. The cubic root of 21320305 is about 277.2880398570.

Adding to 21320305 its reverse (50302312), we get a palindrome (71622617).

The spelling of 21320305 in words is "twenty-one million, three hundred twenty thousand, three hundred five".