21206323 has 2 divisors, whose sum is σ = 21206324. Its totient is φ = 21206322.

The previous prime is 21206303. The next prime is 21206347. The reversal of 21206323 is 32360212.

21206323 is nontrivially palindromic in base 12.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21206323 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21206323.

It is not a weakly prime, because it can be changed into another prime (21206303) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10603161 + 10603162.

It is an arithmetic number, because the mean of its divisors is an integer number (10603162).

Almost surely, 2^21206323 is an apocalyptic number.

21206323 is a deficient number, since it is larger than the sum of its proper divisors (1).

21206323 is an equidigital number, since it uses as much as digits as its factorization.

21206323 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 19.

The square root of 21206323 is about 4605.0323560210. The cubic root of 21206323 is about 276.7930135325.

Adding to 21206323 its reverse (32360212), we get a palindrome (53566535).

The spelling of 21206323 in words is "twenty-one million, two hundred six thousand, three hundred twenty-three".