21306023 has 2 divisors, whose sum is σ = 21306024. Its totient is φ = 21306022.

The previous prime is 21305989. The next prime is 21306079. The reversal of 21306023 is 32060312.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21306023 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21305992 and 21306010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21306823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10653011 + 10653012.

It is an arithmetic number, because the mean of its divisors is an integer number (10653012).

Almost surely, 2^21306023 is an apocalyptic number.

21306023 is a deficient number, since it is larger than the sum of its proper divisors (1).

21306023 is an equidigital number, since it uses as much as digits as its factorization.

21306023 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216, while the sum is 17.

The square root of 21306023 is about 4615.8447764196. The cubic root of 21306023 is about 277.2261096547.

Adding to 21306023 its reverse (32060312), we get a palindrome (53366335).

The spelling of 21306023 in words is "twenty-one million, three hundred six thousand, twenty-three".