21011220100 has 144 divisors (see below), whose sum is σ = 50199912000. Its totient is φ = 7586219520.

The previous prime is 21011220089. The next prime is 21011220121. The reversal of 21011220100 is 102211012.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 12977091 + ... + 12978709.

It is an arithmetic number, because the mean of its divisors is an integer number (348610500).

Almost surely, 2^21011220100 is an apocalyptic number.

21011220100 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 21011220100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25099956000).

21011220100 is an abundant number, since it is smaller than the sum of its proper divisors (29188691900).

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

21011220100 is a wasteful number, since it uses less digits than its factorization.

21011220100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1862 (or 1855 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21011220100 its reverse (102211012), we get a palindrome (21113431112).

The spelling of 21011220100 in words is "twenty-one billion, eleven million, two hundred twenty thousand, one hundred".