21663305 has 8 divisors (see below), whose sum is σ = 26021832. Its totient is φ = 17313408.

The previous prime is 21663283. The next prime is 21663329. The reversal of 21663305 is 50336612.

It can be written as a sum of positive squares in 4 ways, for example, as 4910656 + 16752649 = 2216^2 + 4093^2 .

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 21663305 - 2¹⁰ = 21662281 is a prime.

It is a Duffinian number.

It is a Curzon 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, 6629 + ... + 9341.

It is an arithmetic number, because the mean of its divisors is an integer number (3252729).

Almost surely, 2^21663305 is an apocalyptic number.

It is an amenable number.

21663305 is a deficient number, since it is larger than the sum of its proper divisors (4358527).

21663305 is a wasteful number, since it uses less digits than its factorization.

21663305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4315.

The product of its (nonzero) digits is 3240, while the sum is 26.

The square root of 21663305 is about 4654.3855663234. The cubic root of 21663305 is about 278.7671348231.

Adding to 21663305 its reverse (50336612), we get a palindrome (71999917).

The spelling of 21663305 in words is "twenty-one million, six hundred sixty-three thousand, three hundred five".