21056563 has 8 divisors (see below), whose sum is σ = 23025600. Its totient is φ = 19096680.

The previous prime is 21056561. The next prime is 21056573. The reversal of 21056563 is 36565012.

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 21056563 - 2¹ = 21056561 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21056561) 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, 3088 + ... + 7186.

It is an arithmetic number, because the mean of its divisors is an integer number (2878200).

Almost surely, 2^21056563 is an apocalyptic number.

21056563 is a deficient number, since it is larger than the sum of its proper divisors (1969037).

21056563 is a wasteful number, since it uses less digits than its factorization.

21056563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4577.

The product of its (nonzero) digits is 5400, while the sum is 28.

The square root of 21056563 is about 4588.7430740890. The cubic root of 21056563 is about 276.1398987954.

It can be divided in two parts, 2105 and 6563, that added together give a palindrome (8668).

The spelling of 21056563 in words is "twenty-one million, fifty-six thousand, five hundred sixty-three".