21305423 has 2 divisors, whose sum is σ = 21305424. Its totient is φ = 21305422.

The previous prime is 21305419. The next prime is 21305461. The reversal of 21305423 is 32450312.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21305423 - 2² = 21305419 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21305395 and 21305404.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21305413) by changing a digit.

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 as a sum of consecutive naturals, namely, 10652711 + 10652712.

It is an arithmetic number, because the mean of its divisors is an integer number (10652712).

Almost surely, 2^21305423 is an apocalyptic number.

21305423 is a deficient number, since it is larger than the sum of its proper divisors (1).

21305423 is an equidigital number, since it uses as much as digits as its factorization.

21305423 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 20.

The square root of 21305423 is about 4615.7797824420. The cubic root of 21305423 is about 277.2235073041.

Adding to 21305423 its reverse (32450312), we get a palindrome (53755735).

The spelling of 21305423 in words is "twenty-one million, three hundred five thousand, four hundred twenty-three".