21012220020 has 96 divisors (see below), whose sum is σ = 64257411456. Its totient is φ = 5087948800.

The previous prime is 21012220013. The next prime is 21012220037. The reversal of 21012220020 is 2002221012.

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 = 21012219978 and 21012220005.

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, 563392 + ... + 599528.

It is an arithmetic number, because the mean of its divisors is an integer number (669348036).

Almost surely, 2^21012220020 is an apocalyptic number.

21012220020 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 21012220020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32128705728).

21012220020 is an abundant number, since it is smaller than the sum of its proper divisors (43245191436).

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

21012220020 is a wasteful number, since it uses less digits than its factorization.

21012220020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37041 (or 37039 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 12.

Adding to 21012220020 its reverse (2002221012), we get a palindrome (23014441032).

The spelling of 21012220020 in words is "twenty-one billion, twelve million, two hundred twenty thousand, twenty".