21544416 has 72 divisors (see below), whose sum is σ = 61719840. Its totient is φ = 7128576.

The previous prime is 21544409. The next prime is 21544421. The reversal of 21544416 is 61444512.

21544416 is a `hidden beast` number, since 215 + 4 + 441 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a self number, because there is not a number n which added to its sum of digits gives 21544416.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 68676 + ... + 68988.

It is an arithmetic number, because the mean of its divisors is an integer number (857220).

Almost surely, 2^21544416 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 21544416, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30859920).

21544416 is an abundant number, since it is smaller than the sum of its proper divisors (40175424).

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

21544416 is a wasteful number, since it uses less digits than its factorization.

21544416 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 568 (or 557 counting only the distinct ones).

The product of its digits is 3840, while the sum is 27.

The square root of 21544416 is about 4641.5962771443. The cubic root of 21544416 is about 278.2562377060.

Adding to 21544416 its reverse (61444512), we get a palindrome (82988928).

The spelling of 21544416 in words is "twenty-one million, five hundred forty-four thousand, four hundred sixteen".