21020020020 has 144 divisors (see below), whose sum is σ = 67054635648. Its totient is φ = 5526299520.

The previous prime is 21020020019. The next prime is 21020020027. The reversal of 21020020020 is 2002002012.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21020019984 and 21020020011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020020027) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 314602 + ... + 375518.

It is an arithmetic number, because the mean of its divisors is an integer number (465657192).

Almost surely, 2^21020020020 is an apocalyptic number.

21020020020 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 21020020020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33527317824).

21020020020 is an abundant number, since it is smaller than the sum of its proper divisors (46034615628).

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

21020020020 is a wasteful number, since it uses less digits than its factorization.

21020020020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61012 (or 60998 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 9.

Adding to 21020020020 its reverse (2002002012), we get a palindrome (23022022032).

The spelling of 21020020020 in words is "twenty-one billion, twenty million, twenty thousand, twenty".