21042563 has 2 divisors, whose sum is σ = 21042564.
Its totient is φ = 21042562.
The previous prime is 21042551. The next prime is 21042577. The reversal of 21042563 is 36524012.
Adding to 21042563 its reverse (36524012), we get a palindrome (57566575).
It is a weak prime.
It is a cyclic number.
It is not a de Polignac number, because 21042563 - 210 = 21041539 is a prime.
It is not a weakly prime, because it can be changed into another prime (21042533) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521281 + 10521282.
It is an arithmetic number, because the mean of its divisors is an integer number (10521282).
Almost surely, 221042563 is an apocalyptic number.
21042563 is a deficient number, since it is larger than the sum of its proper divisors (1).
21042563 is an equidigital number, since it uses as much as digits as its factorization.
21042563 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 1440, while the sum is 23.
The square root of 21042563 is about 4587.2173482407.
The cubic root of 21042563 is about 276.0786856447.
The spelling of 21042563 in words is "twenty-one million, forty-two thousand, five hundred sixty-three".