21001122120 has 128 divisors (see below), whose sum is σ = 69153315840. Its totient is φ = 5059895040.

The previous prime is 21001122073. The next prime is 21001122173. The reversal of 21001122120 is 2122110012.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21001122096 and 21001122105.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 166357 + ... + 263963.

It is an arithmetic number, because the mean of its divisors is an integer number (540260280).

Almost surely, 2^21001122120 is an apocalyptic number.

21001122120 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 21001122120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34576657920).

21001122120 is an abundant number, since it is smaller than the sum of its proper divisors (48152193720).

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

21001122120 is a wasteful number, since it uses less digits than its factorization.

21001122120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97795 (or 97791 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21001122120 its reverse (2122110012), we get a palindrome (23123232132).

The spelling of 21001122120 in words is "twenty-one billion, one million, one hundred twenty-two thousand, one hundred twenty".