21989717568 has 672 divisors, whose sum is σ = 82819768320. Its totient is φ = 5596231680.

The previous prime is 21989717551. The next prime is 21989717569. The reversal of 21989717568 is 86571798912.

It is a tau number, because it is divible by the number of its divisors (672).

It is a Harshad number since it is a multiple of its sum of digits (63).

Its product of digits (15240960) is a multiple of the sum of its prime factors (432).

It is not an unprimeable number, because it can be changed into a prime (21989717569) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 63370771 + ... + 63371117.

Almost surely, 2^21989717568 is an apocalyptic number.

21989717568 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 21989717568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41409884160).

21989717568 is an abundant number, since it is smaller than the sum of its proper divisors (60830050752).

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

21989717568 is a wasteful number, since it uses less digits than its factorization.

21989717568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 432 (or 403 counting only the distinct ones).

The product of its digits is 15240960, while the sum is 63.

The spelling of 21989717568 in words is "twenty-one billion, nine hundred eighty-nine million, seven hundred seventeen thousand, five hundred sixty-eight".