21563212 has 24 divisors (see below), whose sum is σ = 42173712. Its totient is φ = 9561600.

The previous prime is 21563189. The next prime is 21563219. The reversal of 21563212 is 21236512.

It is a super-2 number, since 2×21563212² = 929944223513888, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is not an unprimeable number, because it can be changed into a prime (21563219) 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, 4173 + ... + 7780.

It is an arithmetic number, because the mean of its divisors is an integer number (1757238).

Almost surely, 2^21563212 is an apocalyptic number.

21563212 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21563212 is a deficient number, since it is larger than the sum of its proper divisors (20610500).

21563212 is a wasteful number, since it uses less digits than its factorization.

21563212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12009 (or 12007 counting only the distinct ones).

The product of its digits is 720, while the sum is 22.

The square root of 21563212 is about 4643.6205702017. The cubic root of 21563212 is about 278.3371339037.

Adding to 21563212 its reverse (21236512), we get a palindrome (42799724).

The spelling of 21563212 in words is "twenty-one million, five hundred sixty-three thousand, two hundred twelve".