21065709868 has 192 divisors, whose sum is σ = 48833003520. Its totient is φ = 7732454400.

The previous prime is 21065709781. The next prime is 21065709877. The reversal of 21065709868 is 86890756012.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 63642463 + ... + 63642793.

It is an arithmetic number, because the mean of its divisors is an integer number (254338560).

Almost surely, 2^21065709868 is an apocalyptic number.

21065709868 is a gapful number since it is divisible by the number (28) 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 21065709868, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24416501760).

21065709868 is an abundant number, since it is smaller than the sum of its proper divisors (27767293652).

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

21065709868 is a wasteful number, since it uses less digits than its factorization.

21065709868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 636 (or 634 counting only the distinct ones).

The product of its (nonzero) digits is 1451520, while the sum is 52.

The spelling of 21065709868 in words is "twenty-one billion, sixty-five million, seven hundred nine thousand, eight hundred sixty-eight".