21991881024 has 168 divisors, whose sum is σ = 66009885760. Its totient is φ = 7258927104.

The previous prime is 21991881019. The next prime is 21991881049. The reversal of 21991881024 is 42018819912.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1594992 + ... + 1608720.

Almost surely, 2^21991881024 is an apocalyptic number.

21991881024 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 21991881024, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33004942880).

21991881024 is an abundant number, since it is smaller than the sum of its proper divisors (44018004736).

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

21991881024 is a wasteful number, since it uses less digits than its factorization.

21991881024 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13859 (or 13837 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 45.

The spelling of 21991881024 in words is "twenty-one billion, nine hundred ninety-one million, eight hundred eighty-one thousand, twenty-four".