21011012220 has 192 divisors, whose sum is σ = 65605478400. Its totient is φ = 4981616640.

The previous prime is 21011012177. The next prime is 21011012273. The reversal of 21011012220 is 2221011012.

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 = 21011012196 and 21011012205.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 5681412 + ... + 5685108.

It is an arithmetic number, because the mean of its divisors is an integer number (341695200).

Almost surely, 2^21011012220 is an apocalyptic number.

21011012220 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 21011012220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32802739200).

21011012220 is an abundant number, since it is smaller than the sum of its proper divisors (44594466180).

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

21011012220 is a wasteful number, since it uses less digits than its factorization.

21011012220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3908 (or 3906 counting only the distinct ones).

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

Adding to 21011012220 its reverse (2221011012), we get a palindrome (23232023232).

The spelling of 21011012220 in words is "twenty-one billion, eleven million, twelve thousand, two hundred twenty".