21333144 has 64 divisors (see below), whose sum is σ = 63613440. Its totient is φ = 5829120.

The previous prime is 21333139. The next prime is 21333163. The reversal of 21333144 is 44133312.

It is a Harshad number since it is a multiple of its sum of digits (21).

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 21333144.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1104 + ... + 6624.

It is an arithmetic number, because the mean of its divisors is an integer number (993960).

Almost surely, 2^21333144 is an apocalyptic number.

21333144 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21333144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31806720).

21333144 is an abundant number, since it is smaller than the sum of its proper divisors (42280296).

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

21333144 is a wasteful number, since it uses less digits than its factorization.

21333144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5560 (or 5556 counting only the distinct ones).

The product of its digits is 864, while the sum is 21.

The square root of 21333144 is about 4618.7816575370. The cubic root of 21333144 is about 277.3436892603.

Adding to 21333144 its reverse (44133312), we get a palindrome (65466456).

The spelling of 21333144 in words is "twenty-one million, three hundred thirty-three thousand, one hundred forty-four".