21020200020 has 144 divisors (see below), whose sum is σ = 66637613952. Its totient is φ = 5353286400.

The previous prime is 21020199989. The next prime is 21020200057. The reversal of 21020200020 is 2000202012.

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 = 21020199975 and 21020200011.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2898519 + ... + 2905761.

It is an arithmetic number, because the mean of its divisors is an integer number (462761208).

Almost surely, 2^21020200020 is an apocalyptic number.

21020200020 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 21020200020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33318806976).

21020200020 is an abundant number, since it is smaller than the sum of its proper divisors (45617413932).

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

21020200020 is a wasteful number, since it uses less digits than its factorization.

21020200020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7982 (or 7977 counting only the distinct ones).

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

Adding to 21020200020 its reverse (2000202012), we get a palindrome (23020402032).

The spelling of 21020200020 in words is "twenty-one billion, twenty million, two hundred thousand, twenty".