21666844794240 has 640 divisors, whose sum is σ = 78073793740800. Its totient is φ = 5725842296832.

The previous prime is 21666844794239. The next prime is 21666844794263. The reversal of 21666844794240 is 4249744866612.

It is a tau number, because it is divible by the number of its divisors (640).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 9473914377 + ... + 9473916663.

It is an arithmetic number, because the mean of its divisors is an integer number (121990302720).

Almost surely, 2^{21666844794240} is an apocalyptic number.

21666844794240 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 21666844794240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39036896870400).

21666844794240 is an abundant number, since it is smaller than the sum of its proper divisors (56406948946560).

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

21666844794240 is a wasteful number, since it uses less digits than its factorization.

21666844794240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3884 (or 3863 counting only the distinct ones).

The product of its (nonzero) digits is 111476736, while the sum is 63.

The spelling of 21666844794240 in words is "twenty-one trillion, six hundred sixty-six billion, eight hundred forty-four million, seven hundred ninety-four thousand, two hundred forty".