21115533563 has 4 divisors (see below), whose sum is σ = 21843655440. Its totient is φ = 20387411688.

The previous prime is 21115533559. The next prime is 21115533583. The reversal of 21115533563 is 36533551112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21115533563 - 2² = 21115533559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21115533583) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 364060895 + ... + 364060952.

It is an arithmetic number, because the mean of its divisors is an integer number (5460913860).

Almost surely, 2^21115533563 is an apocalyptic number.

21115533563 is a deficient number, since it is larger than the sum of its proper divisors (728121877).

21115533563 is an equidigital number, since it uses as much as digits as its factorization.

21115533563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 728121876.

The product of its digits is 40500, while the sum is 35.

The spelling of 21115533563 in words is "twenty-one billion, one hundred fifteen million, five hundred thirty-three thousand, five hundred sixty-three".