21000001221100 has 216 divisors, whose sum is σ = 51482667398400. Its totient is φ = 7426759296000.

The previous prime is 21000001221079. The next prime is 21000001221137. The reversal of 21000001221100 is 112210000012.

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 71 ways as a sum of consecutive naturals, for example, 65531061 + ... + 65850739.

It is an arithmetic number, because the mean of its divisors is an integer number (238345682400).

Almost surely, 2^{21000001221100} is an apocalyptic number.

21000001221100 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 21000001221100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25741333699200).

21000001221100 is an abundant number, since it is smaller than the sum of its proper divisors (30482666177300).

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

21000001221100 is a wasteful number, since it uses less digits than its factorization.

21000001221100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319865 (or 319847 counting only the distinct ones).

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

Adding to 21000001221100 its reverse (112210000012), we get a palindrome (21112211221112).

The spelling of 21000001221100 in words is "twenty-one trillion, one million, two hundred twenty-one thousand, one hundred".