21111122220 has 96 divisors (see below), whose sum is σ = 60778238976. Its totient is φ = 5471884800.

The previous prime is 21111122183. The next prime is 21111122237. The reversal of 21111122220 is 2222111112.

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 21111122220.

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, 650827 + ... + 682493.

It is an arithmetic number, because the mean of its divisors is an integer number (633106656).

Almost surely, 2^21111122220 is an apocalyptic number.

21111122220 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 21111122220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30389119488).

21111122220 is an abundant number, since it is smaller than the sum of its proper divisors (39667116756).

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

21111122220 is a wasteful number, since it uses less digits than its factorization.

21111122220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31991 (or 31989 counting only the distinct ones).

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

Adding to 21111122220 its reverse (2222111112), we get a palindrome (23333233332).

The spelling of 21111122220 in words is "twenty-one billion, one hundred eleven million, one hundred twenty-two thousand, two hundred twenty".