21115224 has 96 divisors (see below), whose sum is σ = 65257920. Its totient is φ = 6110208.

The previous prime is 21115189. The next prime is 21115229. The reversal of 21115224 is 42251112.

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

It is a junction number, because it is equal to n+sod(n) for n = 21115197 and 21115206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21115229) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15249 + ... + 16575.

It is an arithmetic number, because the mean of its divisors is an integer number (679770).

Almost surely, 2^21115224 is an apocalyptic number.

21115224 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21115224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32628960).

21115224 is an abundant number, since it is smaller than the sum of its proper divisors (44142696).

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

21115224 is a wasteful number, since it uses less digits than its factorization.

21115224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1369 (or 1362 counting only the distinct ones).

The product of its digits is 160, while the sum is 18.

The square root of 21115224 is about 4595.1304660477. The cubic root of 21115224 is about 276.3960916566.

Adding to 21115224 its reverse (42251112), we get a palindrome (63366336).

The spelling of 21115224 in words is "twenty-one million, one hundred fifteen thousand, two hundred twenty-four".