21191768064 has 144 divisors (see below), whose sum is σ = 64807011360. Its totient is φ = 6648299520.

The previous prime is 21191768053. The next prime is 21191768071. The reversal of 21191768064 is 46086719112.

It is a tau number, because it is divible by the number of its divisors (144).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 279529 + ... + 347159.

It is an arithmetic number, because the mean of its divisors is an integer number (450048690).

Almost surely, 2^21191768064 is an apocalyptic number.

21191768064 is a gapful number since it is divisible by the number (24) 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 21191768064, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32403505680).

21191768064 is an abundant number, since it is smaller than the sum of its proper divisors (43615243296).

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

21191768064 is a wasteful number, since it uses less digits than its factorization.

21191768064 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67676 (or 67653 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The spelling of 21191768064 in words is "twenty-one billion, one hundred ninety-one million, seven hundred sixty-eight thousand, sixty-four".