21000563 has 2 divisors, whose sum is σ = 21000564. Its totient is φ = 21000562.

The previous prime is 21000557. The next prime is 21000583. The reversal of 21000563 is 36500012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21000563 - 2⁸ = 21000307 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21000533) 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, 10500281 + 10500282.

It is an arithmetic number, because the mean of its divisors is an integer number (10500282).

Almost surely, 2^21000563 is an apocalyptic number.

21000563 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000563 is an equidigital number, since it uses as much as digits as its factorization.

21000563 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 21000563 is about 4582.6371228802. The cubic root of 21000563 is about 275.8948831309.

Adding to 21000563 its reverse (36500012), we get a palindrome (57500575).

The spelling of 21000563 in words is "twenty-one million, five hundred sixty-three", and thus it is an aban number.