21945056 has 36 divisors (see below), whose sum is σ = 49534632. Its totient is φ = 9374976.

The previous prime is 21945043. The next prime is 21945067. The reversal of 21945056 is 65054912.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 69956 + ... + 70268.

It is an arithmetic number, because the mean of its divisors is an integer number (1375962).

Almost surely, 2^21945056 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 21945056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24767316).

21945056 is an abundant number, since it is smaller than the sum of its proper divisors (27589576).

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

21945056 is an frugal number, since it uses more digits than its factorization.

21945056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 643 (or 322 counting only the distinct ones).

The product of its (nonzero) digits is 10800, while the sum is 32.

The square root of 21945056 is about 4684.5550482410. Note that the first 3 decimals coincide. The cubic root of 21945056 is about 279.9704730769.

Adding to 21945056 its reverse (65054912), we get a palindrome (86999968).

The spelling of 21945056 in words is "twenty-one million, nine hundred forty-five thousand, fifty-six".