21231111220 has 96 divisors (see below), whose sum is σ = 49745404800. Its totient is φ = 7546613760.

The previous prime is 21231111211. The next prime is 21231111241. The reversal of 21231111220 is 2211113212.

It is a junction number, because it is equal to n+sod(n) for n = 21231111194 and 21231111203.

It is a congruent number.

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, 1808931 + ... + 1820629.

It is an arithmetic number, because the mean of its divisors is an integer number (518181300).

Almost surely, 2^21231111220 is an apocalyptic number.

21231111220 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 21231111220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24872702400).

21231111220 is an abundant number, since it is smaller than the sum of its proper divisors (28514293580).

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

21231111220 is a wasteful number, since it uses less digits than its factorization.

21231111220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11905 (or 11903 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 16.

Adding to 21231111220 its reverse (2211113212), we get a palindrome (23442224432).

The spelling of 21231111220 in words is "twenty-one billion, two hundred thirty-one million, one hundred eleven thousand, two hundred twenty".