21091889664 has 480 divisors, whose sum is σ = 69861242880. Its totient is φ = 6083444736.

The previous prime is 21091889659. The next prime is 21091889671. The reversal of 21091889664 is 46698819012.

It is a self number, because there is not a number n which added to its sum of digits gives 21091889664.

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 47 ways as a sum of consecutive naturals, for example, 55070017 + ... + 55070399.

It is an arithmetic number, because the mean of its divisors is an integer number (145544256).

Almost surely, 2^21091889664 is an apocalyptic number.

21091889664 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 21091889664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34930621440).

21091889664 is an abundant number, since it is smaller than the sum of its proper divisors (48769353216).

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

21091889664 is a wasteful number, since it uses less digits than its factorization.

21091889664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 480 (or 461 counting only the distinct ones).

The product of its (nonzero) digits is 1492992, while the sum is 54.

The spelling of 21091889664 in words is "twenty-one billion, ninety-one million, eight hundred eighty-nine thousand, six hundred sixty-four".