21231563 has 16 divisors (see below), whose sum is σ = 22619520. Its totient is φ = 19905600.

The previous prime is 21231557. The next prime is 21231577. The reversal of 21231563 is 36513212.

It is a cyclic number.

It is not a de Polignac number, because 21231563 - 2⁴ = 21231547 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21231503) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 162008 + ... + 162138.

It is an arithmetic number, because the mean of its divisors is an integer number (1413720).

Almost surely, 2^21231563 is an apocalyptic number.

21231563 is a deficient number, since it is larger than the sum of its proper divisors (1387957).

21231563 is a wasteful number, since it uses less digits than its factorization.

21231563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 298.

The product of its digits is 1080, while the sum is 23.

The square root of 21231563 is about 4607.7720212701. The cubic root of 21231563 is about 276.9027840286.

Adding to 21231563 its reverse (36513212), we get a palindrome (57744775).

The spelling of 21231563 in words is "twenty-one million, two hundred thirty-one thousand, five hundred sixty-three".