21001221001200 has 960 divisors, whose sum is σ = 77897584664064. Its totient is φ = 4790016000000.

The previous prime is 21001221001169. The next prime is 21001221001207. The reversal of 21001221001200 is 210012210012.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001221001207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 2121116250 + ... + 2121126150.

Almost surely, 2^{21001221001200} is an apocalyptic number.

21001221001200 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 21001221001200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38948792332032).

21001221001200 is an abundant number, since it is smaller than the sum of its proper divisors (56896363662864).

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

21001221001200 is a wasteful number, since it uses less digits than its factorization.

21001221001200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10114 (or 10103 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21001221001200 its reverse (210012210012), we get a palindrome (21211233211212).

21001221001200 divided by its reverse (210012210012) gives a square (100 = 10²).

It can be divided in two parts, 210012 and 21001200, that multiplied together give a square (4410504014400 = 2100120²).

The spelling of 21001221001200 in words is "twenty-one trillion, one billion, two hundred twenty-one million, one thousand, two hundred".