21563263 has 4 divisors (see below), whose sum is σ = 21572568. Its totient is φ = 21553960.

The previous prime is 21563257. The next prime is 21563273. The reversal of 21563263 is 36236512.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21563263 is a prime.

It is a super-2 number, since 2×21563263² = 929948622414338, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21563273) 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, 1908 + ... + 6838.

It is an arithmetic number, because the mean of its divisors is an integer number (5393142).

Almost surely, 2^21563263 is an apocalyptic number.

21563263 is a deficient number, since it is larger than the sum of its proper divisors (9305).

21563263 is an equidigital number, since it uses as much as digits as its factorization.

21563263 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9304.

The product of its digits is 6480, while the sum is 28.

The square root of 21563263 is about 4643.6260616032. The cubic root of 21563263 is about 278.3373533389.

Adding to 21563263 its reverse (36236512), we get a palindrome (57799775).

The spelling of 21563263 in words is "twenty-one million, five hundred sixty-three thousand, two hundred sixty-three".