21318563 has 8 divisors (see below), whose sum is σ = 24616032. Its totient is φ = 18084096.

The previous prime is 21318541. The next prime is 21318599. The reversal of 21318563 is 36581312.

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 21318563 - 2¹⁰ = 21317539 is a prime.

It is a super-2 number, since 2×21318563² = 908962256769938, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21318533) 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, 15020 + ... + 16377.

It is an arithmetic number, because the mean of its divisors is an integer number (3077004).

Almost surely, 2^21318563 is an apocalyptic number.

21318563 is a deficient number, since it is larger than the sum of its proper divisors (3297469).

21318563 is an equidigital number, since it uses as much as digits as its factorization.

21318563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31501.

The product of its digits is 4320, while the sum is 29.

The square root of 21318563 is about 4617.2029411755. The cubic root of 21318563 is about 277.2804876054.

Adding to 21318563 its reverse (36581312), we get a palindrome (57899875).

The spelling of 21318563 in words is "twenty-one million, three hundred eighteen thousand, five hundred sixty-three".