21112121220 has 192 divisors, whose sum is σ = 62890007040. Its totient is φ = 5283532800.

The previous prime is 21112121207. The next prime is 21112121221. The reversal of 21112121220 is 2212121112.

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 21112121220.

It is not an unprimeable number, because it can be changed into a prime (21112121221) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 9017250 + ... + 9019590.

It is an arithmetic number, because the mean of its divisors is an integer number (327552120).

Almost surely, 2^21112121220 is an apocalyptic number.

21112121220 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 21112121220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31445003520).

21112121220 is an abundant number, since it is smaller than the sum of its proper divisors (41777885820).

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

21112121220 is a wasteful number, since it uses less digits than its factorization.

21112121220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2526 (or 2524 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21112121220 its reverse (2212121112), we get a palindrome (23324242332).

The spelling of 21112121220 in words is "twenty-one billion, one hundred twelve million, one hundred twenty-one thousand, two hundred twenty".