21366563 has 8 divisors (see below), whose sum is σ = 22356000. Its totient is φ = 20382208.

The previous prime is 21366557. The next prime is 21366581. The reversal of 21366563 is 36566312.

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 21366563 - 2⁴ = 21366547 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21366503) 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, 9293 + ... + 11361.

It is an arithmetic number, because the mean of its divisors is an integer number (2794500).

Almost surely, 2^21366563 is an apocalyptic number.

21366563 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21366563 is a deficient number, since it is larger than the sum of its proper divisors (989437).

21366563 is a wasteful number, since it uses less digits than its factorization.

21366563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2541.

The product of its digits is 19440, while the sum is 32.

The square root of 21366563 is about 4622.3979707507. The cubic root of 21366563 is about 277.4884360628.

The spelling of 21366563 in words is "twenty-one million, three hundred sixty-six thousand, five hundred sixty-three".