21101021100020 has 96 divisors (see below), whose sum is σ = 45533570977440. Its totient is φ = 8209053941760.

The previous prime is 21101021099993. The next prime is 21101021100037. The reversal of 21101021100020 is 2000112010112.

It can be written as a sum of positive squares in 16 ways, for example, as 2270524594276 + 18830496505744 = 1506826^2 + 4339412^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21101021099974 and 21101021100010.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 643366262 + ... + 643399058.

It is an arithmetic number, because the mean of its divisors is an integer number (474308031015).

Almost surely, 2^{21101021100020} is an apocalyptic number.

21101021100020 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 21101021100020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22766785488720).

21101021100020 is an abundant number, since it is smaller than the sum of its proper divisors (24432549877420).

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

21101021100020 is a wasteful number, since it uses less digits than its factorization.

21101021100020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35253 (or 35251 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21101021100020 its reverse (2000112010112), we get a palindrome (23101133110132).

The spelling of 21101021100020 in words is "twenty-one trillion, one hundred one billion, twenty-one million, one hundred thousand, twenty".