21021100020 has 48 divisors (see below), whose sum is σ = 65398979520. Its totient is φ = 5605626528.

The previous prime is 21021100019. The next prime is 21021100073. The reversal of 21021100020 is 2000112012.

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 = 21021099975 and 21021100011.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19463442 + ... + 19464521.

It is an arithmetic number, because the mean of its divisors is an integer number (1362478740).

Almost surely, 2^21021100020 is an apocalyptic number.

21021100020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21021100020 is an abundant number, since it is smaller than the sum of its proper divisors (44377879500).

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

21021100020 is a wasteful number, since it uses less digits than its factorization.

21021100020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38927981 (or 38927973 counting only the distinct ones).

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

Adding to 21021100020 its reverse (2000112012), we get a palindrome (23021212032).

The spelling of 21021100020 in words is "twenty-one billion, twenty-one million, one hundred thousand, twenty".