21065311680 has 168 divisors, whose sum is σ = 77802108048. Its totient is φ = 4814917632.

The previous prime is 21065311661. The next prime is 21065311681. The reversal of 21065311680 is 8611356012.

It is a tau number, because it is divible by the number of its divisors (168).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21065311681) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 176869 + ... + 270948.

It is an arithmetic number, because the mean of its divisors is an integer number (463107786).

Almost surely, 2^21065311680 is an apocalyptic number.

21065311680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21065311680 is an abundant number, since it is smaller than the sum of its proper divisors (56736796368).

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

21065311680 is a wasteful number, since it uses less digits than its factorization.

21065311680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 447851 (or 447834 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 33.

Adding to 21065311680 its reverse (8611356012), we get a palindrome (29676667692).

The spelling of 21065311680 in words is "twenty-one billion, sixty-five million, three hundred eleven thousand, six hundred eighty".