21303216 has 80 divisors (see below), whose sum is σ = 66721920. Its totient is φ = 6454080.

The previous prime is 21303209. The next prime is 21303229. The reversal of 21303216 is 61230312.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2511 + ... + 6993.

It is an arithmetic number, because the mean of its divisors is an integer number (834024).

Almost surely, 2^21303216 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 21303216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33360960).

21303216 is an abundant number, since it is smaller than the sum of its proper divisors (45418704).

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

21303216 is a wasteful number, since it uses less digits than its factorization.

21303216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4511 (or 4499 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 21303216 is about 4615.5407050529. The cubic root of 21303216 is about 277.2139345706.

Adding to 21303216 its reverse (61230312), we get a palindrome (82533528).

The spelling of 21303216 in words is "twenty-one million, three hundred three thousand, two hundred sixteen".