21564216 has 48 divisors (see below), whose sum is σ = 59515560. Its totient is φ = 7051200.

The previous prime is 21564203. The next prime is 21564217. The reversal of 21564216 is 61246512.

21564216 is a `hidden beast` number, since 2 + 1 + 5 + 642 + 16 = 666.

It is a super-3 number, since 3×21564216³ (a number of 23 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21564216.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21564217) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 991 + ... + 6641.

Almost surely, 2^21564216 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 21564216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29757780).

21564216 is an abundant number, since it is smaller than the sum of its proper divisors (37951344).

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

21564216 is a wasteful number, since it uses less digits than its factorization.

21564216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5716 (or 5709 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21564216 is about 4643.7286742444. The cubic root of 21564216 is about 278.3414537015.

The spelling of 21564216 in words is "twenty-one million, five hundred sixty-four thousand, two hundred sixteen".