21245056 has 64 divisors (see below), whose sum is σ = 49008960. Its totient is φ = 8985600.

The previous prime is 21245051. The next prime is 21245057. The reversal of 21245056 is 65054212.

It is a tau number, because it is divible by the number of its divisors (64).

It is a self number, because there is not a number n which added to its sum of digits gives 21245056.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21245051) 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 in 7 ways as a sum of consecutive naturals, for example, 117286 + ... + 117466.

It is an arithmetic number, because the mean of its divisors is an integer number (765765).

Almost surely, 2^21245056 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 21245056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24504480).

21245056 is an abundant number, since it is smaller than the sum of its proper divisors (27763904).

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

21245056 is a wasteful number, since it uses less digits than its factorization.

21245056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333 (or 321 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 25.

The square root of 21245056 is about 4609.2359453601. The cubic root of 21245056 is about 276.9614303321.

Adding to 21245056 its reverse (65054212), we get a palindrome (86299268).

The spelling of 21245056 in words is "twenty-one million, two hundred forty-five thousand, fifty-six".