21816216 has 80 divisors (see below), whose sum is σ = 61811640. Its totient is φ = 7188480.

The previous prime is 21816209. The next prime is 21816217. The reversal of 21816216 is 61261812.

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

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 21816216.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21816217) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 84760 + ... + 85016.

Almost surely, 2^21816216 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 21816216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30905820).

21816216 is an abundant number, since it is smaller than the sum of its proper divisors (39995424).

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

21816216 is a wasteful number, since it uses less digits than its factorization.

21816216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 406 (or 393 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 21816216 is about 4670.7832319644. The cubic root of 21816216 is about 279.4214926453.

The spelling of 21816216 in words is "twenty-one million, eight hundred sixteen thousand, two hundred sixteen".