20001221100 has 216 divisors, whose sum is σ = 72320871168. Its totient is φ = 4528828800.

The previous prime is 20001221083. The next prime is 20001221137. The reversal of 20001221100 is 112210002.

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

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 659265 + ... + 688935.

It is an arithmetic number, because the mean of its divisors is an integer number (334818848).

Almost surely, 2^20001221100 is an apocalyptic number.

20001221100 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 20001221100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36160435584).

20001221100 is an abundant number, since it is smaller than the sum of its proper divisors (52319650068).

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

20001221100 is a wasteful number, since it uses less digits than its factorization.

20001221100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29805 (or 29795 counting only the distinct ones).

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

Adding to 20001221100 its reverse (112210002), we get a palindrome (20113431102).

The spelling of 20001221100 in words is "twenty billion, one million, two hundred twenty-one thousand, one hundred".