21011220984 has 128 divisors (see below), whose sum is σ = 59615942400. Its totient is φ = 6117534720.

The previous prime is 21011220983. The next prime is 21011221019. The reversal of 21011220984 is 48902211012.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011220983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7070619 + ... + 7073589.

It is an arithmetic number, because the mean of its divisors is an integer number (465749550).

Almost surely, 2^21011220984 is an apocalyptic number.

21011220984 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 21011220984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29807971200).

21011220984 is an abundant number, since it is smaller than the sum of its proper divisors (38604721416).

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

21011220984 is a wasteful number, since it uses less digits than its factorization.

21011220984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4205 (or 4201 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 30.

Adding to 21011220984 its reverse (48902211012), we get a palindrome (69913431996).

The spelling of 21011220984 in words is "twenty-one billion, eleven million, two hundred twenty thousand, nine hundred eighty-four".