21205538563 has 8 divisors (see below), whose sum is σ = 24350857920. Its totient is φ = 18263143080.

The previous prime is 21205538533. The next prime is 21205538567. The reversal of 21205538563 is 36583550212.

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 21205538563 - 2²⁵ = 21171984131 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21205538567) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 50730745 + ... + 50731162.

It is an arithmetic number, because the mean of its divisors is an integer number (3043857240).

Almost surely, 2^21205538563 is an apocalyptic number.

21205538563 is a deficient number, since it is larger than the sum of its proper divisors (3145319357).

21205538563 is a wasteful number, since it uses less digits than its factorization.

21205538563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101461937.

The product of its (nonzero) digits is 216000, while the sum is 40.

The spelling of 21205538563 in words is "twenty-one billion, two hundred five million, five hundred thirty-eight thousand, five hundred sixty-three".