21206923 has 2 divisors, whose sum is σ = 21206924. Its totient is φ = 21206922.

The previous prime is 21206909. The next prime is 21206947. The reversal of 21206923 is 32960212.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21206923 - 2⁵ = 21206891 is a prime.

It is not a weakly prime, because it can be changed into another prime (21206953) 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 as a sum of consecutive naturals, namely, 10603461 + 10603462.

It is an arithmetic number, because the mean of its divisors is an integer number (10603462).

Almost surely, 2^21206923 is an apocalyptic number.

21206923 is a deficient number, since it is larger than the sum of its proper divisors (1).

21206923 is an equidigital number, since it uses as much as digits as its factorization.

21206923 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 21206923 is about 4605.0975016822. The cubic root of 21206923 is about 276.7956239841.

The spelling of 21206923 in words is "twenty-one million, two hundred six thousand, nine hundred twenty-three".