21101200020 has 72 divisors (see below), whose sum is σ = 67772099304. Its totient is φ = 5295986688.

The previous prime is 21101200007. The next prime is 21101200033. The reversal of 21101200020 is 2000210112.

It is an interprime number because it is at equal distance from previous prime (21101200007) and next prime (21101200033).

It can be written as a sum of positive squares in 4 ways, for example, as 8276996484 + 12824203536 = 90978^2 + 113244^2 .

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 = 21101199975 and 21101200011.

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 23 ways as a sum of consecutive naturals, for example, 3444849 + ... + 3450968.

It is an arithmetic number, because the mean of its divisors is an integer number (941279157).

Almost surely, 2^21101200020 is an apocalyptic number.

21101200020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21101200020 is an abundant number, since it is smaller than the sum of its proper divisors (46670899284).

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

21101200020 is a wasteful number, since it uses less digits than its factorization.

21101200020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6895849 (or 6895844 counting only the distinct ones).

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

Adding to 21101200020 its reverse (2000210112), we get a palindrome (23101410132).

The spelling of 21101200020 in words is "twenty-one billion, one hundred one million, two hundred thousand, twenty".