21666113280 has 1008 divisors, whose sum is σ = 92652263424. Its totient is φ = 4747714560.

The previous prime is 21666113279. The next prime is 21666113297. The reversal of 21666113280 is 8231166612.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (1008).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 202486987 + ... + 202487093.

It is an arithmetic number, because the mean of its divisors is an integer number (91916928).

Almost surely, 2^21666113280 is an apocalyptic number.

21666113280 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 21666113280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46326131712).

21666113280 is an abundant number, since it is smaller than the sum of its proper divisors (70986150144).

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

21666113280 is an equidigital number, since it uses as much as digits as its factorization.

21666113280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184 (or 155 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

Adding to 21666113280 its reverse (8231166612), we get a palindrome (29897279892).

The spelling of 21666113280 in words is "twenty-one billion, six hundred sixty-six million, one hundred thirteen thousand, two hundred eighty".