21840000 has 320 divisors, whose sum is σ = 89221440. Its totient is φ = 4608000.

The previous prime is 21839989. The next prime is 21840023. The reversal of 21840000 is 4812.

It is a tau number, because it is divible by the number of its divisors (320).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1679994 + ... + 1680006.

It is an arithmetic number, because the mean of its divisors is an integer number (278817).

Almost surely, 2^21840000 is an apocalyptic number.

21840000 is a gapful number since it is divisible by the number (20) 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 21840000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44610720).

21840000 is an abundant number, since it is smaller than the sum of its proper divisors (67381440).

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

21840000 is an equidigital number, since it uses as much as digits as its factorization.

21840000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57 (or 30 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

The square root of 21840000 is about 4673.3285782192. The cubic root of 21840000 is about 279.5229973727.

Adding to 21840000 its reverse (4812), we get a palindrome (21844812).

It can be divided in two parts, 21 and 840000, that multiplied together give a square (17640000 = 4200²).

The spelling of 21840000 in words is "twenty-one million, eight hundred forty thousand".