21121012320 has 96 divisors (see below), whose sum is σ = 66632842080. Its totient is φ = 5623664640.

The previous prime is 21121012307. The next prime is 21121012357. The reversal of 21121012320 is 2321012112.

It is a tau number, because it is divible by the number of its divisors (96).

It is a super-2 number, since 2×21121012320² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21121012320.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 283996 + ... + 350564.

It is an arithmetic number, because the mean of its divisors is an integer number (694092105).

Almost surely, 2^21121012320 is an apocalyptic number.

21121012320 is a gapful number since it is divisible by the number (20) 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 21121012320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33316421040).

21121012320 is an abundant number, since it is smaller than the sum of its proper divisors (45511829760).

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

21121012320 is a wasteful number, since it uses less digits than its factorization.

21121012320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67248 (or 67240 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 15.

Adding to 21121012320 its reverse (2321012112), we get a palindrome (23442024432).

The spelling of 21121012320 in words is "twenty-one billion, one hundred twenty-one million, twelve thousand, three hundred twenty".