21100220100 has 216 divisors, whose sum is σ = 69772582880. Its totient is φ = 5318784000.

The previous prime is 21100220069. The next prime is 21100220101. The reversal of 21100220100 is 102200112.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is not an unprimeable number, because it can be changed into a prime (21100220101) 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 71 ways as a sum of consecutive naturals, for example, 9763020 + ... + 9765180.

Almost surely, 2^21100220100 is an apocalyptic number.

21100220100 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 21100220100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34886291440).

21100220100 is an abundant number, since it is smaller than the sum of its proper divisors (48672362780).

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

21100220100 is a wasteful number, since it uses less digits than its factorization.

21100220100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2771 (or 2761 counting only the distinct ones).

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

Adding to 21100220100 its reverse (102200112), we get a palindrome (21202420212).

It can be divided in two parts, 21 and 100220100, that added together give a square (100220121 = 10011²).

The spelling of 21100220100 in words is "twenty-one billion, one hundred million, two hundred twenty thousand, one hundred".