21206325680 has 80 divisors (see below), whose sum is σ = 51492132864. Its totient is φ = 8106827520.

The previous prime is 21206325677. The next prime is 21206325689. The reversal of 21206325680 is 8652360212.

It is a tau number, because it is divible by the number of its divisors (80).

It is a self number, because there is not a number n which added to its sum of digits gives 21206325680.

It is not an unprimeable number, because it can be changed into a prime (21206325689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2511065 + ... + 2519495.

Almost surely, 2^21206325680 is an apocalyptic number.

21206325680 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 21206325680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25746066432).

21206325680 is an abundant number, since it is smaller than the sum of its proper divisors (30285807184).

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

21206325680 is a wasteful number, since it uses less digits than its factorization.

21206325680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9834 (or 9828 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 35.

Adding to 21206325680 its reverse (8652360212), we get a palindrome (29858685892).

The spelling of 21206325680 in words is "twenty-one billion, two hundred six million, three hundred twenty-five thousand, six hundred eighty".