21225472 has 28 divisors (see below), whose sum is σ = 42464736. Its totient is φ = 10608640.

The previous prime is 21225437. The next prime is 21225473. The reversal of 21225472 is 27452212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21225473) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6897 + ... + 9487.

Almost surely, 2^21225472 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 21225472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21232368).

21225472 is an abundant number, since it is smaller than the sum of its proper divisors (21239264).

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

21225472 is an frugal number, since it uses more digits than its factorization.

21225472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2617 (or 2593 counting only the distinct ones).

The product of its digits is 2240, while the sum is 25.

The square root of 21225472 is about 4607.1110253607. Note that the first 3 decimals coincide. The cubic root of 21225472 is about 276.8763018179.

Adding to 21225472 its reverse (27452212), we get a palindrome (48677684).

The spelling of 21225472 in words is "twenty-one million, two hundred twenty-five thousand, four hundred seventy-two".