21004563 has 8 divisors (see below), whose sum is σ = 28037376. Its totient is φ = 13987400.

The previous prime is 21004549. The next prime is 21004579. The reversal of 21004563 is 36540012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21004563 - 2⁴ = 21004547 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21004513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 303 + ... + 6488.

It is an arithmetic number, because the mean of its divisors is an integer number (3504672).

Almost surely, 2^21004563 is an apocalyptic number.

21004563 is a deficient number, since it is larger than the sum of its proper divisors (7032813).

21004563 is a wasteful number, since it uses less digits than its factorization.

21004563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7825.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21004563 is about 4583.0735320307. The cubic root of 21004563 is about 275.9123986847.

Adding to 21004563 its reverse (36540012), we get a palindrome (57544575).

The spelling of 21004563 in words is "twenty-one million, four thousand, five hundred sixty-three".