21000220020 has 144 divisors (see below), whose sum is σ = 72636192720. Its totient is φ = 4865200128.

The previous prime is 21000220019. The next prime is 21000220039. The reversal of 21000220020 is 2002200012.

It can be written as a sum of positive squares in 8 ways, for example, as 4462774416 + 16537445604 = 66804^2 + 128598^2 .

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 = 21000219984 and 21000220011.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 224175 + ... + 303734.

It is an arithmetic number, because the mean of its divisors is an integer number (504418005).

Almost surely, 2^21000220020 is an apocalyptic number.

21000220020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21000220020 is an abundant number, since it is smaller than the sum of its proper divisors (51635972700).

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

21000220020 is a wasteful number, since it uses less digits than its factorization.

21000220020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 527954 (or 527949 counting only the distinct ones).

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

Adding to 21000220020 its reverse (2002200012), we get a palindrome (23002420032).

The spelling of 21000220020 in words is "twenty-one billion, two hundred twenty thousand, twenty".