21266563 has 8 divisors (see below), whose sum is σ = 21644480. Its totient is φ = 20891520.

The previous prime is 21266561. The next prime is 21266603. The reversal of 21266563 is 36566212.

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 21266563 - 2¹ = 21266561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21266561) 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, 18481 + ... + 19597.

It is an arithmetic number, because the mean of its divisors is an integer number (2705560).

Almost surely, 2^21266563 is an apocalyptic number.

21266563 is a deficient number, since it is larger than the sum of its proper divisors (377917).

21266563 is a wasteful number, since it uses less digits than its factorization.

21266563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1437.

The product of its digits is 12960, while the sum is 31.

The square root of 21266563 is about 4611.5683883035. The cubic root of 21266563 is about 277.0548575682.

The spelling of 21266563 in words is "twenty-one million, two hundred sixty-six thousand, five hundred sixty-three".