21333816 has 72 divisors (see below), whose sum is σ = 67223520. Its totient is φ = 6094368.

The previous prime is 21333779. The next prime is 21333839. The reversal of 21333816 is 61833312.

It is a happy number.

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

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 21333816.

It is a congruent number.

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 17 ways as a sum of consecutive naturals, for example, 505 + ... + 6551.

It is an arithmetic number, because the mean of its divisors is an integer number (933660).

Almost surely, 2^21333816 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 21333816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33611760).

21333816 is an abundant number, since it is smaller than the sum of its proper divisors (45889704).

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

21333816 is a wasteful number, since it uses less digits than its factorization.

21333816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6073 (or 6059 counting only the distinct ones).

The product of its digits is 2592, while the sum is 27.

The square root of 21333816 is about 4618.8544034208. The cubic root of 21333816 is about 277.3466013643.

The spelling of 21333816 in words is "twenty-one million, three hundred thirty-three thousand, eight hundred sixteen".