21606840720 has 480 divisors, whose sum is σ = 78063253632. Its totient is φ = 5550944256.

The previous prime is 21606840719. The next prime is 21606840743. The reversal of 21606840720 is 2704860612.

21606840720 is a `hidden beast` number, since 2 + 1 + 606 + 8 + 40 + 7 + 2 + 0 = 666.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 69031284 + ... + 69031596.

Almost surely, 2^21606840720 is an apocalyptic number.

21606840720 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 21606840720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39031626816).

21606840720 is an abundant number, since it is smaller than the sum of its proper divisors (56456412912).

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

21606840720 is a wasteful number, since it uses less digits than its factorization.

21606840720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 461 (or 443 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 36.

The spelling of 21606840720 in words is "twenty-one billion, six hundred six million, eight hundred forty thousand, seven hundred twenty".