21991181184 has 576 divisors, whose sum is σ = 78218300160. Its totient is φ = 6129478656.

The previous prime is 21991181183. The next prime is 21991181203. The reversal of 21991181184 is 48118119912.

It is a tau number, because it is divible by the number of its divisors (576).

It is a super-2 number, since 2×21991181184² (a number of 21 digits) contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21991181183) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 71632359 + ... + 71632665.

It is an arithmetic number, because the mean of its divisors is an integer number (135795660).

Almost surely, 2^21991181184 is an apocalyptic number.

21991181184 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 21991181184, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39109150080).

21991181184 is an abundant number, since it is smaller than the sum of its proper divisors (56227118976).

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

21991181184 is an equidigital number, since it uses as much as digits as its factorization.

21991181184 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 397 (or 366 counting only the distinct ones).

The product of its digits is 41472, while the sum is 45.

The spelling of 21991181184 in words is "twenty-one billion, nine hundred ninety-one million, one hundred eighty-one thousand, one hundred eighty-four".