21101020020 has 120 divisors (see below), whose sum is σ = 68477409000. Its totient is φ = 5432894208.

The previous prime is 21101019959. The next prime is 21101020051. The reversal of 21101020020 is 2002010112.

It can be written as a sum of positive squares in 4 ways, for example, as 4019052816 + 17081967204 = 63396^2 + 130698^2 .

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 = 21101019984 and 21101020011.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 177595 + ... + 271554.

It is an arithmetic number, because the mean of its divisors is an integer number (570645075).

Almost surely, 2^21101020020 is an apocalyptic number.

21101020020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21101020020 is an abundant number, since it is smaller than the sum of its proper divisors (47376388980).

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

21101020020 is a wasteful number, since it uses less digits than its factorization.

21101020020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 449199 (or 449188 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21101020020 its reverse (2002010112), we get a palindrome (23103030132).

The spelling of 21101020020 in words is "twenty-one billion, one hundred one million, twenty thousand, twenty".