21225564 has 84 divisors (see below), whose sum is σ = 57841560. Its totient is φ = 6804000.

The previous prime is 21225563. The next prime is 21225583. The reversal of 21225564 is 46552212.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21225563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 84439 + ... + 84689.

It is an arithmetic number, because the mean of its divisors is an integer number (688590).

Almost surely, 2^21225564 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 21225564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28920780).

21225564 is an abundant number, since it is smaller than the sum of its proper divisors (36615996).

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

21225564 is a wasteful number, since it uses less digits than its factorization.

21225564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 302 (or 285 counting only the distinct ones).

The product of its digits is 4800, while the sum is 27.

The square root of 21225564 is about 4607.1210099150. The cubic root of 21225564 is about 276.8767018496.

Adding to 21225564 its reverse (46552212), we get a palindrome (67777776).

The spelling of 21225564 in words is "twenty-one million, two hundred twenty-five thousand, five hundred sixty-four".