21101100820 has 24 divisors (see below), whose sum is σ = 44366984928. Its totient is φ = 8430026400.

The previous prime is 21101100817. The next prime is 21101100821. The reversal of 21101100820 is 2800110112.

It is a junction number, because it is equal to n+sod(n) for n = 21101100794 and 21101100803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21101100821) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 634246 + ... + 666685.

It is an arithmetic number, because the mean of its divisors is an integer number (1848624372).

Almost surely, 2^21101100820 is an apocalyptic number.

21101100820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21101100820 is an abundant number, since it is smaller than the sum of its proper divisors (23265884108).

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

21101100820 is a wasteful number, since it uses less digits than its factorization.

21101100820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1301751 (or 1301749 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 16.

Adding to 21101100820 its reverse (2800110112), we get a palindrome (23901210932).

The spelling of 21101100820 in words is "twenty-one billion, one hundred one million, one hundred thousand, eight hundred twenty".