21218112 has 70 divisors (see below), whose sum is σ = 62912498. Its totient is φ = 7070976.

The previous prime is 21218089. The next prime is 21218143. The reversal of 21218112 is 21181212.

It can be written as a sum of positive squares in only one way, i.e., 17438976 + 3779136 = 4176^2 + 1944^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nude number because it is divisible by every one of its digits and also a Zuckerman number because it is divisible by the product of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 3138 + ... + 7230.

Almost surely, 2^21218112 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21218112, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31456249).

21218112 is an abundant number, since it is smaller than the sum of its proper divisors (41694386).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21218112 is an equidigital number, since it uses as much as digits as its factorization.

21218112 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4117 (or 4098 counting only the distinct ones).

The product of its digits is 64, while the sum is 18.

The square root of 21218112 is about 4606.3121908963. The cubic root of 21218112 is about 276.8442955385.

Adding to 21218112 its reverse (21181212), we get a palindrome (42399324).

The spelling of 21218112 in words is "twenty-one million, two hundred eighteen thousand, one hundred twelve".