21326563 has 2 divisors, whose sum is σ = 21326564. Its totient is φ = 21326562.

The previous prime is 21326561. The next prime is 21326573. The reversal of 21326563 is 36562312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21326563 - 2¹ = 21326561 is a prime.

Together with 21326561, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21326561) 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, 10663281 + 10663282.

It is an arithmetic number, because the mean of its divisors is an integer number (10663282).

Almost surely, 2^21326563 is an apocalyptic number.

21326563 is a deficient number, since it is larger than the sum of its proper divisors (1).

21326563 is an equidigital number, since it uses as much as digits as its factorization.

21326563 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6480, while the sum is 28.

The square root of 21326563 is about 4618.0691852765. The cubic root of 21326563 is about 277.3151673426.

Adding to 21326563 its reverse (36562312), we get a palindrome (57888875).

The spelling of 21326563 in words is "twenty-one million, three hundred twenty-six thousand, five hundred sixty-three".