21304205 has 8 divisors (see below), whose sum is σ = 27531672. Its totient is φ = 15732288.

The previous prime is 21304147. The next prime is 21304219. The reversal of 21304205 is 50240312.

It can be written as a sum of positive squares in 4 ways, for example, as 391876 + 20912329 = 626^2 + 4573^2 .

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

It is not a de Polignac number, because 21304205 - 2¹⁶ = 21238669 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent 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, 163814 + ... + 163943.

It is an arithmetic number, because the mean of its divisors is an integer number (3441459).

Almost surely, 2^21304205 is an apocalyptic number.

It is an amenable number.

21304205 is a deficient number, since it is larger than the sum of its proper divisors (6227467).

21304205 is a wasteful number, since it uses less digits than its factorization.

21304205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 327775.

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

The square root of 21304205 is about 4615.6478418528. The cubic root of 21304205 is about 277.2182243820.

Adding to 21304205 its reverse (50240312), we get a palindrome (71544517).

The spelling of 21304205 in words is "twenty-one million, three hundred four thousand, two hundred five".