21021020020 has 192 divisors, whose sum is σ = 61184212992. Its totient is φ = 5852736000.

The previous prime is 21021019997. The next prime is 21021020057. The reversal of 21021020020 is 2002012012.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21021019979 and 21021020006.

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, 603685 + ... + 637555.

It is an arithmetic number, because the mean of its divisors is an integer number (318667776).

Almost surely, 2^21021020020 is an apocalyptic number.

21021020020 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 21021020020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30592106496).

21021020020 is an abundant number, since it is smaller than the sum of its proper divisors (40163192972).

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

21021020020 is a wasteful number, since it uses less digits than its factorization.

21021020020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33942 (or 33940 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

Adding to 21021020020 its reverse (2002012012), we get a palindrome (23023032032).

The spelling of 21021020020 in words is "twenty-one billion, twenty-one million, twenty thousand, twenty".