21306323 has 4 divisors (see below), whose sum is σ = 21318528. Its totient is φ = 21294120.

The previous prime is 21306317. The next prime is 21306343. The reversal of 21306323 is 32360312.

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

It is a cyclic number.

It is not a de Polignac number, because 21306323 - 2¹² = 21302227 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21306295 and 21306304.

It is not an unprimeable number, because it can be changed into a prime (21306343) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2936 + ... + 7157.

It is an arithmetic number, because the mean of its divisors is an integer number (5329632).

Almost surely, 2^21306323 is an apocalyptic number.

21306323 is a deficient number, since it is larger than the sum of its proper divisors (12205).

21306323 is a wasteful number, since it uses less digits than its factorization.

21306323 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12204.

The product of its (nonzero) digits is 648, while the sum is 20.

The square root of 21306323 is about 4615.8772730652. The cubic root of 21306323 is about 277.2274108117.

Adding to 21306323 its reverse (32360312), we get a palindrome (53666635).

The spelling of 21306323 in words is "twenty-one million, three hundred six thousand, three hundred twenty-three".