21232224 has 144 divisors (see below), whose sum is σ = 66869712. Its totient is φ = 6349824.

The previous prime is 21232223. The next prime is 21232229. The reversal of 21232224 is 42223212.

It is a tau number, because it is divible by the number of its divisors (144).

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.

It is a junction number, because it is equal to n+sod(n) for n = 21232197 and 21232206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21232223) 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, 198379 + ... + 198485.

It is an arithmetic number, because the mean of its divisors is an integer number (464373).

Almost surely, 2^21232224 is an apocalyptic number.

21232224 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 21232224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33434856).

21232224 is an abundant number, since it is smaller than the sum of its proper divisors (45637488).

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

21232224 is a wasteful number, since it uses less digits than its factorization.

21232224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189 (or 178 counting only the distinct ones).

The product of its digits is 384, while the sum is 18.

The square root of 21232224 is about 4607.8437473508. The cubic root of 21232224 is about 276.9056575938.

Adding to 21232224 its reverse (42223212), we get a palindrome (63455436).

The spelling of 21232224 in words is "twenty-one million, two hundred thirty-two thousand, two hundred twenty-four".